Processes for the preparation of carfilzomib or pharmaceutically acceptable salts thereof

ABSTRACT

The present invention relates to an improved process for the preparation of carfilzomib or a pharmaceutically acceptable salt thereof. The present invention also relates to a process for the preparation of amorphous form of carfilzomib.

CROSS-REFERENCE TO RELATED APPLICATIONS

-   -   This application is a divisional application of and claims the        benefit of the filing date of U.S. patent application Ser. No.        15/573,912, filed Nov. 14, 2017, which is a national phase        application of and claims the benefit of International        Application PCT/IB2016/052994, filed on 21 May 2016, which is        based on and claims the benefit of Indian Provisional        Application No. 2543/CHE/2015, filed on 21 May 2015 entitled “An        improved process for the preparation of carfilzomib or        pharmaceutically acceptable salts thereof”, and claims the        benefit of Indian Provisional Application No. 2592/CHE/2015,        filed on 25 May 2015 entitled “An improved process for        preparation of tert-butyl        ((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)        carbamate”, and claims the benefit of Indian Provisional        Application No. 3106/CHE/2015, filed on 22 Jun. 2015 entitled        “An improved process for the preparation of carfilzomib or        pharmaceutically acceptable salts thereof”, the contents of each        of which are incorporated by reference herein.

FIELD OF THE INVENTION

The present invention generally relates to an improved process for thepreparation of carfilzomib or a pharmaceutically acceptable saltthereof. The present invention also relates to process for preparationof amorphous form of carfilzomib.

The present invention further relates to a process for preparation oftert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamate,a synthetic intermediate for preparation of carfilzomib.

BACKGROUND OF THE INVENTION

Carfilzomib is a tetrapeptide epoxyketone, also known as(2S)—N—((S)-1-((S)-4-methyl-1-((R)-2-methyloxiran2-yl)-1-oxopentan-2-yl-carbamoyl)-2-phenyl-ethyl)-2-((S)-2-(2-morpholinoacetamido)-4-phenylbutanamido)-4-methyl-pentanamide,is represented by the following structure of Formula I:

Carfilzomib is marketed by Onyx Pharma under the trade name Kyprolis® isindicated for the treatment of patients with multiple myeloma who havereceived at least two prior therapies including bortezomib and animmunomodulatory agent and have demonstrated disease progression on orwithin 60 days of completion of the last therapy.

U.S. Pat. No. 7,232,818 (“the '818 patent”) discloses a variety ofpeptide based compounds and their derivatives such as carfilzomib andits process for preparation thereof. The process disclosed in the '818patent is schematically represented as follows:

The synthesis of carfilzomib as disclosed in the '818 patent has certaindrawbacks as it involves:

-   -   a) coupling of N-boc-leucine of Formula II with phenyl alanine        benzyl ester of Formula III in presence of excess quantity of        coupling agents such as PyBOP of about 1.6 w/w mole equivalents        and an additive of HOBt of about 1.6 w/w mole equivalents per        mole of Formula III, in higher volume of solvent such as        acetonitrile of about 45 v for the preparation of compound of        Formula IV;    -   b) coupling of trifluoro acetic acid salt of Formula V with a        compound of Formula VI in presence of excess quantity of        coupling agents such as PyBOP of about 1.6 w/w mole equivalents        and an additive of HOBt of about 1.6 w/w mole equivalents per        mole of Formula IV, in higher volume of solvent such as        acetonitrile of about 22 v for the preparation of compound of        Formula VII;    -   c) coupling of trifluoro acetic acid salt of Formula XIII with        morpholine acetic acid of Formula XII in presence of excess        quantity of coupling agents such as PyBOP of about 1.6 w/w mole        equivalents and an additive of HOBt of about 1.6 w/w mole        equivalents per mole of Formula VII, in higher volume of solvent        such as dimethylformamide of about 24 v for the preparation of        compound of Formula XIV; and    -   d) coupling of Formula XV with a compound of Formula IX in        presence of excess quantity of coupling agents such as PyBOP of        about 1.6 w/w mole equivalents per mole of Formula XV, in higher        volume of solvent such as acetonitrile of about 50 v for the        preparation of carfilzomib;

All the above mentioned amide coupling reactions involves use of excessquantity of coupling agent, excess quantity of an additive and solvent.Use of excess quantity of these reagents results to formation of higherquantity of unreacted HOBt, PyBOP and by product of tris(pyrrolidinophosphine) oxide thereby it necessitates separate purificationtechniques required for the high pure product, which contributessignificant impact on the final yield and purity, thereby process notviable for large scale manufacturing. Further, the process involves longreaction times, which leads to an increase in the manufacturing cycletime and decrease in the product yield and quality.

Further, the '818 patent involves solvent extractions for isolation ofintermediates and final product; which process also isolates unreactedcoupling agents present in the reaction medium along with requiredintermediates and final product. Thereby additional purificationsrequired to separate those unwanted coupling agents.

Journal of biological chemistry vol. 285, no. 51, pp. 40125-40134, 2010discloses preparation of carfilzomib. The process disclosed in thearticle is schematically represented as follows:

U.S. Pat. No. 8,367,617 (“the '617 patent”) disclosed an alternateprocess for preparation of carfilzomib. The process disclosed in the'617 patent is schematically represented as follows:

However, '617 patent disclosed process also involves use of excessquantity of coupling agents same as mentioned for '818 patent.

PCT publication No. 2015/010436 (“the '436 publication”) discloses aprocess for preparation of carfilzomib. The process disclosed in the'436 publication is schematically represented as follows:

PCT publication No. 2015/032621 (“the '621 publication”) discloses aprocess for preparation of carfilzomib. The process disclosed in the'621 publication is schematically represented as follows:

PCT publication No. 2015/032622 (“the '622 publication”) discloses aprocess for preparation of carfilzomib. The process disclosed in the'622 publication is schematically represented as follows:

PCT publication No. 2015/121769 (“the '769 publication”) discloses aprocess for preparation of carfilzomib intermediate. The processdisclosed in the '769 publication is schematically represented asfollows:

PCT publication No. 2016/046843 (“the '843 publication”) discloses aprocess for preparation of carfilzomib. The process disclosed in the'843 publication is schematically represented as follows:

PCT publication No. 2016/069479 (“the '479 publication”) discloses aprocess for preparation of carfilzomib. The process disclosed in the'479 publication is schematically represented as follows:

Kyung et al., in Bioorganic & Medicinal Chemistry Letters 9 (1999)2283-2288 discloses a process for the preparation of carfilzomibintermediate of Formula XVI starting from Weinrebamide of Formula XVII,which involves direct epoxidation of α,β-unsaturated ketone of FormulaXVIII in presence of hydrogen peroxide to obtain diastereomeric mixturein compound of Formula XVI and Formula XVIa in a ratio of 1.7:1.However, this reference silent on isolation of intermediate compoundsobtained from this process. The process disclosed by Kyung et al isschematically represented as follows:

PCT publication No. 2005/111009 (“the '009 publication”) discloses aprocess for preparation of carboxybenzyl (Cbz) protected compound ofFormula XVI, by reduction of Cbz protected α,β-unsaturated ketone ofFormula XVIII there by forming a diastereomeric mixture of allyl alcoholof Formula XIXa and Formula XIXb and epoxidation of allyl group of theobtained diastereomeric mixture of Formula XIX to obtain adiastereomeric mixture of compound of Formula XXa and Formula XXb,further oxidizing the hydroxy group of the obtained a diastereomericmixture of Formula XX and the obtained compound was purified by flashchromatography to obtain diastereomeric mixture of compound of FormulaXVI and Formula XVIa as a light yellow oil in a ratio of 9:1. Theprocess disclosed in the '009 publication is schematically representedas follows:

PCT publication No. 2009/045497 (“the '497 publication”) discloses aprocess for stereoselective epoxidation of α,β-unsaturated ketone ofFormula XVIII in presence of sodium hypochlorite or calcium hypochloriteto obtain diastereomeric mixture of compound of Formula XVI and FormulaXVIa. The process disclosed in the '497 publication is schematicallyrepresented as follows:

Pereira et al., in ChemBioChem 2012, 13, 810-817 discloses a process forthe preparation of compound of Formula XVI starting from boc-Leucine.The process disclosed by Pereira et al is schematically represented asfollows:

Wang et al., in Chemistry—A European Journal 2012, vol. 18, Issue 22,Page-6750-6753 discloses a process for epoxidation of Formula XVIII inpresence of hydrogen peroxide to obtain diastereomeric mixture ofcompound of Formula XVI and Formula XVIa in 1:7 ratio. The processdisclosed by Wang et al is schematically represented as follows:

PCT publication No. 2014/003203 (“the '203 publication”) discloses aprocess for compound of Formula XVI, by reduction of compound of FormulaXVIII in presence of amine borane complex and further converted in todiastereomeric mixture of compound of Formula XVI and Formula XVIa. Theprocess disclosed in the '203 publication is schematically representedas follows:

As compound of Formula XVI and Formula XVIII have almost marginalpolarity differences, compound of Formula XVI is readily isolated alongwith compound of Formula XVIII as an impurity in oily liquid state, thuscompound of Formula XVIII is not possible to separate out from themixture. Thereby unwanted formula XVIII is involved in the furthersequential steps in preparation of carfilzomib, leads to formation ofimpurity of Formula 28.

All the above described processes involve isolation of intermediatecompound of Formula XVIII, Formula XIX and Formula XVI as an oilynature, which are having higher content of process impurities therebyusing such impure intermediates in the preparation of carfilzomib leadsto formation of impure product.

Further, numerous CN publication No.(s) 103641890, 103864889, 103864898,103936828, 103804469, 104086624, 104230857, 104356197, 104557793,104672179, 104672180, 104710507, 105017181, 105273057, 105294501,105218488 and 105440106 discloses process for preparation of carfilzomiband its intermediates thereof.

Reported literatures on preparation of carfilzomib involvesN-boc-L-leucine of Formula II, L-phenyl alanine benzyl ester of FormulaIII, N-boc-L-Homophenylalanine of Formula VI and Formula IX asintermediates, which contains traces of its corresponding D-isomers orisoleucine compounds as impurities which tends to react in the samesequential manner to generate the corresponding isomers as impurities,which requires repetitive purifications to separate from the final API.

Different isomers of a chiral drug molecule bind differently to targetreceptors, one isomer of a drug may have a desired beneficial effectwhile the other may cause serious and undesired side effects orsometimes even beneficial but entirely different effect, hence in thedrug molecule the effective isomer is preferred in pure form, free ofother undesired isomers, thus carfilzomib free of its other isomerswould always be preferred.

Presence of impurities in a pharmaceutical compound is undesirable andhealth authorities in many jurisdictions (e.g. the Food and DrugAdministration in the United States) have established guidelinesrelating to acceptable levels of impurities in pharmaceuticals. The needfor and commercial utility of methods of reducing the level ofimpurities in any pharmaceutical are self-evident.

Based on the drawbacks mentioned above, there is a vital need to developa process for the preparation of carfilzomib or a pharmaceuticallyacceptable salt thereof and its intermediates, which is readily amenableto large scale production with higher purity and yield.

Hence, present inventors focused research to simplify the process forthe preparation of carfilzomib or a pharmaceutically acceptable saltthereof, which avoids mainly usage of excess quantity of reagents andsolvents as compared to the prior-art processes, thereby making theprocess more suitable for commercial applications with higher purity,yield and obviate the problems associated with the reported process.

The present invention further relates to crystalline maleate salt ofcarfilzomib and its process for preparation thereof. The presentinvention furthermore relates to process for preparation of amorphousform of carfilzomib.

The present invention also relates to process for preparation of highlypure compound of Formula XVI and its intermediates in solid state, whichis necessary for obtaining high pure carfilzomib API.

SUMMARY OF THE INVENTION

In accordance with one embodiment, the present invention provides animproved process for the preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof:

comprising:

-   -   a) reacting a compound of Formula II with a compound of Formula        III or a salt thereof in presence of a coupling agent (C1), an        additive (A1) and a base (B1) in a suitable solvent (S1) to        obtain a compound of Formula IV,

-   -   b) reacting the compound of Formula IV with a suitable acid to        obtain a compound of Formula V or a salt thereof,

-   -   c) reacting the compound of Formula V or a salt thereof with a        compound of Formula VI in presence of a coupling agent (C2), an        additive (A2) and a base (B2) in a suitable solvent (S2) to        obtain a compound of Formula VII,

-   -   d) deprotecting the compound of Formula VII in presence of a        suitable deprotecting agent to obtain a compound of Formula        VIII,

-   -   e) reacting the compound of Formula VIII with a compound of        Formula IX or a salt threof in presence of a coupling agent        (C3), an additive (A3) and a base (B3) in a suitable solvent        (S3) to obtain a compound of Formula X,

-   -   f) reacting the compound of Formula X with a suitable acid to        obtain a compound of Formula XI or a salt thereof, and

-   -   g) reacting the compound of Formula XI or a salt thereof with a        compound of Formula XII or a salt thereof in presence of a        coupling agent (C4), an additive (A4) and a base (B4) in a        suitable solvent (S4) to obtain carfilzomib or a        pharmaceutically acceptable salt thereof,

wherein the coupling agent (C1), (C2), (C3) and (C4) are used in anamount of about 0.9 to about 1.3 w/w mole equivalents per mole ofFormula III, Formula IV, Formula VIII and Formula X respectively;

wherein the additive (A1), (A2), (A3) and (A4) are used in catalyticamount of about 0.05 to about 0.5 w/w mole equivalents per mole ofFormula III, Formula IV, Formula VIII and Formula X respectively.

In accordance another embodiment, the present invention provides animproved process for the preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof; comprising:

-   -   a) reacting a compound of Formula VIII with a compound of        Formula IX or a salt threof in presence of a coupling agent        (C3), an additive (A3) and a base (B3) in a suitable solvent        (S3) to obtain a compound of Formula X,    -   b) reacting the compound of Formula X with a suitable acid to        obtain a compound of Formula XI or a salt thereof, and    -   c) reacting the compound of Formula XI or a salt thereof with a        compound of Formula XII or a salt thereof in presence of a        coupling agent (C4), an additive (A4) and a base (B4) in a        suitable solvent (S4) to obtain carfilzomib or a        pharmaceutically acceptable salt thereof,

wherein the coupling agent (C3) and (C4) are used in an amount of about0.9 to about 1.3 w/w mole equivalents per mole of Formula VIII andFormula X respectively;

wherein the additive (A3) and (A4) are used in catalytic amount of about0.05 to about 0.5 w/w mole equivalents per mole of Formula VIII andFormula X respectively.

In accordance another embodiment, the present invention provides animproved process for the preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof; comprising:

-   -   a) reacting a compound of Formula X with a suitable acid to        obtain a compound of Formula XI or a salt thereof, and    -   b) reacting the compound of Formula XI or a salt thereof with a        compound of Formula XII or a salt thereof in presence of a        coupling agent (C4), an additive (A4) and a base (B4) in a        suitable solvent (S4) to obtain carfilzomib or a        pharmaceutically acceptable salt thereof,

wherein the coupling agent C4 is used in an amount of about 0.9 to about1.3 w/w mole equivalents per mole of Formula X;

wherein the additive A4 is used in catalytic amount of about 0.05 toabout 0.5 w/w mole equivalents per mole of Formula X.

In accordance another embodiment, the present invention provides animproved process for the preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof; comprising: reacting acompound of Formula XI or a salt thereof with a compound of Formula XIIor a salt thereof in presence of a coupling agent (C4), an additive (A4)and a base (B4) in a suitable solvent (S4) to obtain carfilzomib or apharmaceutically acceptable salt thereof.

In accordance with another embodiment, the present invention provides animproved process for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof; comprising: reacting acompound of Formula XI or a salt thereof with a compound of Formula XIIor a salt threof in presence of a coupling agent (C4), an additive (A4)and a base (B4) in a suitable solvent (S4) to obtain carfilzomib or apharmaceutically acceptable salt thereof; wherein the coupling agent(C4) is used in an amount of about 0.9 to about 1.3 w/w mole equivalentsper mole of Formula X; wherein the additive (A4) is used in catalyticamount of about 0.05 to about 0.5 w/w mole equivalents per mole ofFormula X.

In accordance another embodiment, the present invention provides animproved process for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof comprising:

-   -   a) reacting a compound of Formula II with a compound of Formula        III or a salt thereof in presence of a coupling agent (C1), an        additive (A1) and a base (B1) in a suitable solvent (S1) to        obtain a compound of Formula IV, wherein the coupling agent (C1)        is used in an amount of about 0.9 to about 1.3 w/w mole        equivalents per mole of Formula III; wherein the additive (A1)        is used in catalytic amount of about 0.05 to about 0.5 w/w mole        equivalents per mole of Formula III, and    -   b) converting the compound of Formula IV into compound of        Formula I or a pharmaceutically acceptable salt thereof.

In accordance with another embodiment, the present invention provides animproved process for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof; comprising:

-   -   a) reacting a compound of Formula V with a compound of Formula        VI in presence of a coupling agent (C2), an additive (A2) and a        base (B2) in a suitable solvent (S2) to obtain a compound of        Formula VII, wherein the coupling agent (C2) is used in an        amount of about 0.9 to about 1.3 w/w mole equivalents per mole        of Formula IV; wherein the additive (A2) is used in catalytic        amount of about 0.05 to about 0.5 w/w mole equivalents per mole        of Formula IV, and    -   b) converting the compound of Formula VII into compound of        Formula I or a pharmaceutically acceptable salt thereof.

In accordance with another embodiment, the present invention provides animproved process for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof comprising:

-   -   a) reacting a compound of Formula VIII with a compound of        Formula IX or a salt threof in presence of a coupling agent        (C3), an additive (A3) and a base (B3) in a suitable solvent        (S3) to obtain a compound of Formula X; wherein the coupling        agent (C3) is used in an amount of about 0.9 to about 1.3 w/w        mole equivalents per mole of Formula VIII; wherein the additive        (A3) is used in catalytic amount of about 0.05 to about 0.5 w/w        mole equivalents per mole of Formula VIII, and    -   b) converting the compound of Formula X into compound of Formula        I or a pharmaceutically acceptable salt thereof.

In accordance with another embodiment, the present invention provides aprocess for purification of compound of Formula X, comprising:

-   -   a) dissolving compound of Formula X in one or more suitable        solvent at a temperature of about 30° C. to about reflux        temperature,    -   b) cooling the obtained solution to less than 10° C., and    -   c) filtering the compound of Formula X.

In another embodiment, the present invention provides a process forpurification of carfilzomib, comprising:

-   -   a) providing a solution of carfilzomib in one or more organic        solvents,    -   b) adding maleic acid to the step a) solution,    -   c) isolating the carfilzomib maleic acid salt,    -   d) neutralizing the carfilzomib maleic acid salt in a suitable        solvent using a base,    -   e) concentrating the step d) solution under vacuum to obtain a        residue,    -   f) dissolving the step e) residue in a suitable solvent,    -   g) adding the step f) solution to an anti-solvent, or        vice-versa, and    -   h) isolating the pure carfilzomib.

In accordance with another embodiment, the present invention provides aprocess for preparation of amorphous Form of carfilzomib, comprising:

-   -   a) providing a solution of carfilzomib pharmaceutically        acceptable salt in a suitable solvent,    -   b) neutralizing the step a) solution with a base,    -   c) concentrating the step b) solution under vacuum to obtain a        residue,    -   d) dissolving the step c) residue in a suitable solvent,    -   e) adding the step d) solution to an anti-solvent, or vice-versa        and    -   f) isolating the amorphous form of carfilzomib.

In accordance with another embodiment, the present invention provides aprocess for preparation of amorphous Form of carfilzomib, comprising:

-   -   a) providing a solution of carfilzomib maleate salt in methylene        chloride,    -   b) neutralizing the step a) solution with a base,    -   c) concentrating the step b) solution under vacuum to obtain a        residue,    -   d) dissolving the step c) residue in methanol,    -   e) adding the step d) solution to water, or vice-versa and    -   f) isolating the amorphous form of carfilzomib.

In accordance with another embodiment, the present invention provides aprocess for preparation of crystalline maleate salt of carfilzomib,comprising:

-   -   a) providing a solution of carfilzomib in one or more organic        solvents,    -   b) adding maleic acid to the step a) solution, and    -   c) isolating the carfilzomib maleate salt.

In accordance with another embodiment, the present invention provides animproved process for the preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof:

comprising:

-   -   a1) reacting a compound of Formula II with a compound of Formula        III or a salt thereof in presence of a coupling agent (C1), an        additive (A1) and a base (B1) in a suitable solvent (S1) to        obtain a compound of Formula IV,

-   -   b1) reacting the compound of Formula IV with a suitable acid to        obtain a compound of Formula V or a salt thereof,

-   -   c1) reacting the compound of Formula V or a salt thereof with a        compound of Formula VI in presence of a coupling agent (C2), an        additive (A2) and a base (B2) in a suitable solvent (S2) to        obtain a compound of Formula VII,

-   -   d1) reacting the compound of Formula VII with a suitable acid to        obtain a compound of Formula XIII or a salt thereof,

-   -   e1) reacting the compound of Formula XIII or a salt thereof with        a compound of Formula XII in presence of a coupling agent (C5),        an additive (A5) and a base (B5) in a suitable solvent (S5) to        obtain a compound of Formula XIV,

-   -   f1) deprotecting the compound of Formula XIV in presence of a        suitable deprotecting agent to obtain a compound of Formula XV,        and

-   -   g1) reacting the compound of Formula XV with a compound of        Formula IX or a salt threof in presence of a coupling agent        (C6), an additive (A6) and a base (B6) in a suitable solvent        (S6) to obtain carfilzomib or a pharmaceutically acceptable salt        thereof,

wherein the coupling agent (C1), (C2), (C5) and (C6) are used in anamount of about 0.9 to about 1.3 w/w mole equivalents per mole ofFormula III, Formula IV, Formula VII and Formula XV respectively;

wherein the additive (A1), (A2), (A5) and (A6) are used in catalyticamount of about 0.05 to about 0.5 w/w mole equivalents per mole ofFormula III, Formula IV, Formula VII and Formula XV respectively.

In accordance with another embodiment, the present invention provides animproved process for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof; comprising:

-   -   a1) reacting a compound of Formula XIII or a salt thereof with a        compound of Formula XII in presence of a coupling agent (C5), an        additive (A5) and a base (B5) in a suitable solvent (S5) to        obtain a compound of Formula XIV, wherein the coupling agent        (C5) is used in an amount of about 0.9 to about 1.3 w/w mole        equivalents per mole of Formula VII; wherein the additive (A5)        is used in catalytic amount of about 0.05 to about 0.5 w/w mole        equivalents per mole of Formula VII, and    -   b1) converting the compound of Formula XIV into compound of        Formula I or a pharmaceutically acceptable salt thereof.

In accordance with another embodiment, the present invention provides animproved process for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof; comprising: reacting acompound of Formula XV with a compound of Formula IX or a salt threof inpresence of a coupling agent (C6), an additive (A6) and a base (B6) in asuitable solvent (S6) to obtain carfilzomib or a pharmaceuticallyacceptable salt thereof; wherein the coupling agent (C6) is used in anamount of about 0.9 to about 1.3 w/w mole equivalents per mole ofFormula XV; wherein the additive (A6) is used in catalytic amount ofabout 0.05 to about 0.5 w/w mole equivalents per mole of Formula XV.

In accordance with another embodiment, the present invention provides aprocess for the purification of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI,

comprising:

-   -   i) providing a solution of tert-butyl        ((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamate        of Formula XVI in a suitable solvent,    -   ii) cooling the step i) solution to less than 5° C.,    -   iii) optionally adding seed compound of Formula XVI to the        step ii) solution, and    -   iv) isolating the pure compound of Formula XVI; wherein the        suitable solvent is selected from aliphatic hydrocarbons, cyclic        hydrocarbons, ethers and the like and mixture thereof.

In accordance with another embodiment, the present invention provides aprocess for the purification of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI having less than 0.1% by HPLC of compound of FormulaXVIII, comprising:

-   -   i) providing a solution of tert-butyl        ((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamate        of Formula XVI in a suitable solvent,    -   ii) cooling the step i) solution to less than 5° C.,    -   iii) optionally adding seed compound of Formula XVI to the        step ii) solution, and    -   iv) isolating the pure compound of Formula XVI; wherein the        suitable solvent is selected from aliphatic hydrocarbons, cyclic        hydrocarbons, ethers and the like and mixture thereof.

In accordance with another embodiment, the present invention provides aprocess for the preparation of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI,

comprising:

-   -   i) reacting a compound of Formula XVII with alkyl magnesium        halide to obtain a compound of Formula XVIII as a crystalline        solid,

-   -   ii) reducing the compound of Formula XVIII in presence of a        suitable reducing agent to obtain a diastereomeric mixture of        compound of Formula XIXa and Formula XIXb as a crystalline        solid,

-   -   iii) epoxidation and followed by oxidation of the diastereomeric        mixture of compound of Formula XIXa and Formula XIXb to obtain a        diastereomeric mixture of compound of Formula XVI and Formula        XVIa,

-   -   iv) separating the compound of Formula XVI from the        diastereomeric mixture of compound of Formula XVI and Formula        XVIa by chromatography,    -   v) crystallizing the compound of Formula XVI from a suitable        solvent, wherein the suitable solvent is selected from aliphatic        hydrocarbons, cyclic hydrocarbons, ethers and the like and        mixture threof, and    -   vi) isolating the compound of Formula XVI as a crystalline        solid.

In accordance with another embodiment, the present invention provides aprocess for preparation of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI,

comprising:

-   -   i) reacting a compound of Formula XVII with alkyl magnesium        halide to obtain a compound of Formula XVIII,    -   ii) crystallizing the compound of Formula XVIII from a suitable        solvent system to obtain crystalline compound of Formula XVIII,

-   -   iii) reducing the crystalline compound of Formula XVIII in        presence of a suitable reducing agent to obtain a diastereomeric        mixture of compound of Formula XIXa and Formula XIXb,    -   iv) crystallizing the mixture of compound of Formula XIXa and        Formula XIXb from a suitable solvent system to obtain a mixture        of crystalline compound of Formula XIXa and Formula XIXb,

-   -   v) epoxidation and followed by oxidation of diastereomeric        mixture of crystalline compound of Formula XIXa and Formula XIXb        to obtain a diastereomeric mixture of compound of Formula XVI        and Formula XVIa,

-   -   vi) separating the compound of Formula XVI from the        diastereomeric mixture of compound of Formula XVI and Formula        XVIa by chromatography, and    -   vii) crystallizing the compound of Formula XVI from a suitable        solvent system to obtain crystalline compound of Formula XVI.

In accordance with another embodiment, the present invention provides aprocess for the preparation of compound of Formula XVIII as crystallinesolid, comprising:

-   -   i) providing a solution of compound of Formula XVIII in a        suitable solvent,    -   ii) optionally cooling the step i) solution to less than 20° C.,    -   iii) adding an anti-solvent to the step ii) solution, and    -   iv) isolating the crystalline compound of Formula XVIII; wherein        the suitable solvent is selected from the group comprising        alcohols, ketones, esters, nitriles and the like and mixture        thereof; and the anti-solvent is selected from the group        comprising aliphatic hydrocarbons, cyclic hydrocarbons, ethers        and the like and water and mixture thereof.

In accordance with another embodiment, the present invention provides aprocess for the preparation of diastereomeric mixture of compound ofFormula XIXa and Formula XIXb as a crystalline solid, comprising:

-   -   i) providing a solution of diastereomeric mixture of a compound        of Formula XIXa and Formula XIXb in a suitable solvent,    -   ii) cooling the step i) solution to less than 10° C.,    -   iii) adding an anti-solvent to the step ii) solution, and    -   iv) isolating the crystalline compound of Formula XIX; wherein        the suitable solvent is selected from the group comprising        alcohols, ketones, esters, nitriles and the like and mixture        thereof; and the anti-solvent is selected from the group        comprising aliphatic hydrocarbons, cyclic hydrocarbons, ethers        and the like and water and mixture thereof.

In accordance with another embodiment, the present invention provides animproved process for the preparation of carfilzomib, comprisingpreparing the tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI as process described above, and converting the tert-butyl((2S)-4-methyl-14(2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI in to carfilzomib.

In accordance with another embodiment, the present invention provides animproved process for the preparation of carfilzomib having less than0.1% of Formula 28 by HPLC, comprising:

-   -   i) providing a solution of tert-butyl        ((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamate        of Formula XVI in a suitable solvent,    -   ii) cooling the step i) solution to less than 5° C.,    -   iii) optionally adding seed compound of Formula XVI to the        step ii) solution,    -   iv) isolating the pure compound of Formula XVI having less than        0.1% by HPLC of compound of Formula XVIII; and    -   v) converting the pure compound of Formula XVI into carfilzomib;        wherein the suitable solvent is selected from aliphatic        hydrocarbons, cyclic hydrocarbons, ethers and the like and        mixture thereof.

In accordance with another embodiment, the present invention providescompound of Formula XVI containing less than 0.1% of compound of FormulaXVIII as measured by HPLC.

In accordance with another embodiment, the present invention providescrystalline tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI characterized by a powder X-Ray diffraction (PXRD)pattern substantially in accordance with FIG. 8.

In accordance with another embodiment, the present invention providescrystalline tert-butyl ((4S)-2,6-dimethyl-3-oxohept-1-en-4-yl))carbamate of Formula XVIII characterized by a powderX-Ray diffraction (PXRD) pattern substantially in accordance with FIG.9.

In accordance with another embodiment, the present invention providescrystalline tert-butylN-[(3R/S,4S)-3-hydroxy-2,6-dimethylhept-1-en-4-yl]carbamate of FormulaXIX characterized by a powder X-Ray diffraction (PXRD) patternsubstantially in accordance with FIG. 10.

In accordance with another embodiment, the present invention providescarfilzomib containing less than 0.05% as measured by HPLC of one ormore of impurities of Formula 1 to Formula 41; preferably 0.03% asmeasured by HPLC.

In accordance with another embodiment, the present invention provides acompound of Formula 41:

In accordance with another embodiment, the present invention providesamorphous compound of Formula IV.

In accordance with another embodiment, the present invention providesamorphous compound of Formula IV characterized by a powder X-Raydiffraction (PXRD) pattern substantially in accordance with FIG. 1.

In accordance with another embodiment, the present invention providesamorphous compound of Formula VII.

In accordance with another embodiment, the present invention providesamorphous compound of Formula VII characterized by a powder X-Raydiffraction (PXRD) pattern substantially in accordance with FIG. 2.

In accordance with another embodiment, the present invention providesamorphous compound of Formula VIII.

In accordance with another embodiment, the present invention providesamorphous compound of Formula VIII characterized by a powder X-Raydiffraction (PXRD) pattern substantially in accordance with FIG. 3.

In accordance with another embodiment, the present invention providescrystalline compound of Formula X.

In accordance with another embodiment, the present invention providescrystalline compound of Formula X characterized by a powder X-Raydiffraction (PXRD) pattern substantially in accordance with FIG. 4.

In accordance with another embodiment, the present invention providesamorphous compound of Formula XI trifluoro acetic acid salt.

In accordance with another embodiment, the present invention providesamorphous compound of Formula XI trifluoro acetic acid saltcharacterized by a powder X-Ray diffraction (PXRD) pattern substantiallyin accordance with FIG. 5.

In accordance with another embodiment, the present invention providesamorphous compound of Formula XI free amine.

In accordance with another embodiment, the present invention providesamorphous compound of Formula XI free amine characterized by a powderX-Ray diffraction (PXRD) pattern substantially in accordance with FIG.6.

In accordance with another embodiment, the present invention providescrystalline carfilzomib maleate salt.

In accordance with another embodiment, the present invention providescrystalline carfilzomib maleate salt characterized by a powder X-Raydiffraction (PXRD) pattern substantially in accordance with FIG. 7.

In accordance with another embodiment, the present invention provides apharmaceutical composition comprising carfilzomib or a pharmaceuticallyacceptable salt thereof prepared by the processes of the presentinvention and at least one pharmaceutically acceptable excipient.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

FIG. 1 is the characteristic powder X-ray diffraction (XRD) pattern ofamorphous compound of Formula IV.

FIG. 2 is the characteristic powder X-ray diffraction (XRD) pattern ofamorphous compound of Formula VII.

FIG. 3 is the characteristic powder X-ray diffraction (XRD) pattern ofamorphous compound of Formula VIII.

FIG. 4 is the characteristic powder X-ray diffraction (XRD) pattern of acrystalline compound of Formula X.

FIG. 5 is the characteristic powder X-ray diffraction (XRD) pattern ofamorphous compound of Formula XI trifluoro acetic acid salt.

FIG. 6 is the characteristic powder X-ray diffraction (XRD) pattern ofamorphous compound of Formula XI free amine.

FIG. 7 is the characteristic powder X-ray diffraction (XRD) pattern ofcrystalline carfilzomib maleate salt.

FIG. 8 is the characteristic powder X-ray diffraction (XRD) pattern ofcrystalline compound of Formula XVI.

FIG. 9 is the characteristic powder X-ray diffraction (XRD) pattern ofcrystalline compound of Formula XVIII.

FIG. 10 is the characteristic powder X-ray diffraction (XRD) pattern ofcrystalline diastereomeric mixture of compound of Formula XIXa andFormula XIXb.

DETAILED DESCRIPTION OF THE INVENTION

The present invention encompasses an improved process for preparation ofcarfilzomib or a pharmaceutically acceptable salt thereof. The presentinvention also relates to a process for preparation of carfilzomibamorphous form.

The present invention further relates to carfilzomib maleate salt, aprocess for its preparation and its use as intermediate in thepreparation of carfilzomib.

In accordance with one embodiment, the present invention provides animproved process for the preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof:

comprising:

-   -   a) reacting a compound of Formula II with a compound of Formula        III or a salt thereof in presence of a coupling agent (C1), an        additive (A1) and a base (B1) in a suitable solvent (S1) to        obtain a compound of Formula IV,

-   -   b) reacting the compound of Formula IV with a suitable acid to        obtain a compound of Formula V or a salt thereof,

-   -   c) reacting the compound of Formula V or a salt thereof with a        compound of Formula VI in presence of a coupling agent (C2), an        additive (A2) and a base (B2) in a suitable solvent (S2) to        obtain a compound of Formula VII,

-   -   d) deprotecting the compound of Formula VII in presence of a        suitable deprotecting agent to obtain a compound of Formula        VIII,

-   -   e) reacting the compound of Formula VIII with a compound of        Formula IX or a salt threof in presence of a coupling agent        (C3), an additive (A3) and a base (B3) in a suitable solvent        (S3) to obtain a compound of Formula X,

-   -   f) reacting the compound of Formula X with a suitable acid to        obtain a compound of Formula XI or a salt thereof, and

-   -   g) reacting the compound of Formula XI or a salt thereof with a        compound of Formula XII or a salt thereof in presence of a        coupling agent (C4), an additive (A4) and a base (B4) in a        suitable solvent (S4) to obtain carfilzomib or a        pharmaceutically acceptable salt thereof,

wherein the coupling agent (C1), (C2), (C3) and (C4) are used in anamount of about 0.9 to about 1.3 w/w mole equivalents per mole ofFormula III, Formula IV, Formula VIII and Formula X respectively;

wherein the additive (A1), (A2), (A3) and (A4) are used in catalyticamount of about 0.05 to about 0.5 w/w mole equivalents per mole ofFormula III, Formula IV, Formula VIII and Formula X respectively.

The compound of Formula II, L-phenyl alanine benzyl ester of Formula IIIor a salt thereof, N-boc-homophenylalanine of Formula VI and morpholineacetic acid of Formula XII are known in the art and can be procured fromcommercially available sources.

The suitable salt of compounds of Formula III, Formula V, Formula IX,Formula XI or Formula XII employed in the aforementioned process is asalt of a mineral or organic acid, such as HCl, HBr, HI, HNO₃, H₂SO₄,acetic acid, trifluoro acetic acid, formic acid and the like.

The '818 patent process involves peptide coupling reactions using excessquantity of coupling agents, additives and solvents. The use of excessquantity of such coupling reagents contaminate in each step with therequired product, also involves formation of by-product such astris(pyrrolidino phosphine) oxide and it necessitates separatepurification techniques to separate out unwanted coupling agents and/orby-products, which contributes significant impact on the final yield andpurity, which makes the process not viable for large scalemanufacturing. Further, the process involves long reaction times, whichleads to an increase in the manufacturing cycle time and decrease in theproduct yield and quality.

Further reported literatures on preparation of carfilzomib involvesN-boc-L-leucine of Formula II, L-phenyl alanine benzyl ester of FormulaIII, N-boc-L-homophenylalanine of Formula VI and Formula IX asintermediates, which contains traces of its corresponding D-isomers orits isoleucine compounds as impurities which tends to react in the samesequential manner to generate the corresponding isomers of Formula 1-41as impurities, which requires repetitive purifications to separate fromthe final API.

To overcome the difficulties associated with the processes describedabove, the inventors of the present invention have surprisingly foundthat use of less quantity of coupling agent and an additivesubstantially reduces the reaction time cycle, for instance about 3-6hours against about overnight as reported thereby reduces the formationof by products for example tris(pyrrolidino phosphine) oxide, otherprocess impurities and minimizing the contamination of un-reactedcoupling agents such as HOBt, PyBOP. The present process also involves,the raw materials used for preparation of carfilzomib such asN-boc-L-leucine of Formula II, L-phenyl alanine benzyl ester of FormulaIII, N-boc-L-homophenylalanine of Formula VI and Formula IX are havingless than 0.1% of its corresponding isomers thereby increasing theisomeric purity of carfilzomib by avoiding the formation of undesiredcarfilzomib isomers as an impurities.

Step a):

The step a) of the aforementioned process involves reaction of acompound of Formula II with a compound of Formula III or a salt thereofin presence of a coupling agent (C1), an additive (A1) and a base (B1)in a suitable solvent (S1) to obtain a compound of Formula IV.

In a preferred embodiment, the present invention provides an improvedprocess for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof, comprising: reacting acompound of Formula II with a compound of Formula III or a salt thereofin presence of a coupling agent (C1), an additive (A1) and a base (B1)in a suitable solvent (S1) to obtain a compound of Formula IV, whereinthe coupling agent (C1) is used in an amount of about 0.9 to about 1.3w/w mole equivalents per mole of Formula III; wherein the additive (A1)is used in catalytic amount of about 0.05 to about 0.5 w/w moleequivalents per mole of Formula III.

In a preferred embodiment, the N-boc-L-leucine of Formula II is havingless than 0.1% of its corresponding D-isomer and isoleucine of Formula Aand Formula B; the L-phenyl alanine benzyl ester of Formula III ishaving less than 0.1% by HPLC of its corresponding D-isomer of FormulaC:

The coupling agent (C1) used herein for reaction of compound of FormulaII with a compound of Formula III or a salt thereof, preferablyhydrochloride salt, is selected from the group consisting ofbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP), benzotriazol-1-yloxy-tris (dimethylamino)-phosphoniumhexafluorophosphate (BOP), bromo-tripyrrolidino-phosphoniumhexafluorophosphate (PyBrOP), Propylphosphonic anhydride (T3P),N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC),1,1′-Carbonyldiimidazole (CDI), diisopropylcarbodiimide (DCI),dicyclohexyl carbodiimide (DCC) and the like and mixture thereof;preferably benzotriazol-1-yl-oxytripyrrolidinophosphoniumhexafluorophosphate (PyBOP).

The additive (A1) used herein for reaction of compound of Formula IIwith a compound of Formula III or a salt thereof, preferablyhydrochloride salt, is selected from the group consisting of1-Hydroxybenzotriazole (HOBt), 1-Hydroxy-7-aza-1H-benzotriazole (HOAt),2-(1H-Benzotriazol-1-yl)-N,N,N′,N′-tetramethylaminiumtetrafluoroborate/hexa fluoro phosphate (TBTU),2-(7-Aza-1H-benzotriazol-1-yl)-N,N,N′,N′-tetramethylaminiumhexafluorophosphate) (HATU) and the like and mixture thereof; preferably1-Hydroxybenzotriazole (HOBt).

In a preferred embodiment, the coupling agent (C1) used herein isbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP) and is used in an amount of about 1.2 w/w mole equivalents permole of Formula III; additive (A1) used herein is 1-hydroxybenzotriazole(HOBt) and is used in an amount of about 0.1 w/w mole equivalents permole of Formula III.

Exemplary bases (B1) used herein for the reaction of compound of FormulaII with a compound of Formula III or a salt thereof, preferablyhydrochloride salt includes but are not limited to diisopropylethylamine, Imidazole or its salts, 1,8-Diazabicyclo[5.4.0]undec-7-en (DBU),tertiary amines or its hydro halide salts thereof selected from thegroup consisting of triethyl amine-hydrochloride and the like andmixtures thereof preferably diisopropylethyl amine.

The reaction of compound of Formula II with a compound of Formula III ora salt thereof, is advantageously carried out in a solvent (S1).Suitable solvent include, but are not limited to ethers, esters,halogenated hydrocarbons, amides, aromatic solvents, nitriles, ormixtures thereof. The ether includes, but are not limited totetrahydrofuran, 2-methyltetrahydrofuran and the like; esters include,but are not limited to methyl acetate, ethyl acetate, propyl acetate,butyl acetate and the like; halogenated hydrocarbons include, but arenot limited to methylene chloride, ethylene chloride, chloroform and thelike; amides includes, but are not limited to dimethyl formamide,dimethyl acetamide, N-methyl pyrrolidinone and the like; aromaticsolvents include, but are not limited to toluene, chlorobenzene and thelike; nitriles include, but are not limited to acetonitrile,propionitrile, benzonitrile and the like and mixtures thereof;preferably dimethyl formamide.

The reaction temperature should be sufficient to effect the couplingreaction. Typically the reaction temperature can be from about −10° C.to about reflux temperature. Preferably the reaction temperature isabout 25° C. to about 50° C. The reaction may take from about 0.5 hoursto about 6 hours depending upon the coupling agent and additive, solventand temperature chosen, preferably about 1 hour to 4 hours.

After completion of the reaction, the compound of Formula IV isadvantageously isolated by quenching the step a) reaction mass in towater to precipitate compound of Formula IV as solid. The precipitatedcompound of Formula IV may be separated by methods known in the art, forexample filtration.

The resultant product may optionally be further dried using conventionalmethods known in the art at a temperature ranging from about 40° C. toabout 60° C. The compound of Formula IV, obtained by the aforementionedprocess have a chemical purity of at least about 95%, as measured byHPLC, preferably at least about 98%, as measured by HPLC and morepreferably at least about 99.5%, as measured by HPLC; and contains lessthan 0.5% of total impurities, which include byproducts of HOBt, PyBOP,tris(pyrrolidino phosphine) oxide, isomer impurities of Formula 1,Formula 2 and Formula 3 as measured by HPLC; preferably less than 0.3%,as measured by HPLC.

In another embodiment, the obtained compound of Formula IV having lessthan 0.1%, as measured by HPLC of each of impurity of Formula 1, Formula2 or Formula 3; preferably less than 0.05%, as measured by HPLC; morepreferably less than 0.03%, as measured by HPLC.

In another embodiment, the compound of Formula IV obtained by theprocess described above is in amorphous in nature.

In another embodiment, the present invention provides amorphous compoundof Formula IV characterized by a powder X-Ray diffraction (PXRD) patternsubstantially in accordance with FIG. 1.

Step b):

The step b) of the aforementioned process involves deprotection of amineprotecting group of Formula IV with a suitable acid to obtain a compoundof Formula V or a salt thereof.

The suitable acid used herein for step b) is selected from the groupconsisting of hydrochloric acid, hydrobromic acid, sulfuric acid,phosphoric acid, acetic acid, trifluoro acetic acid, trichloro aceticacid, methane sulfonic acid and the like and mixture thereof; preferablytrifluoro acetic acid.

The deprotection reaction of compound of Formula IV with a suitable acidcan be carried out in a suitable organic solvent. The suitable organicsolvent includes but is not limited to alcohols, ketones, ethers,halogenated hydrocarbons and mixtures thereof. The alcohols include, butare not limited to methanol, ethanol, isopropanol and the like; ketonesinclude, but are not limited to acetone, methyl isobutyl ketone, methylethyl ketone and the like; ethers include, but are not limited totetrahydrofuran, dimethyl ether, diisopropyl ether, methyl tertiarybutyl ether, 1,4-dioxane and the like; halogenated hydrocarbons include,but are not limited to methylene chloride, ethylene chloride and thelike and mixture thereof preferably methylene chloride.

The reaction can be carried out at a temperature of about 0° C. toreflux temperature; preferably at 0° C. to about 50° C. After completionof the reaction, the reaction mass can be basified with a suitableaqueous base such as sodium carbonate, potassium carbonate and the likeand then extracting the product with water immiscible organic solventsuch as ethyl acetate, methylene chloride and the like; preferablymethylene chloride. The free base of compound of Formula V can beisolated from the resultant water immiscible organic solvent bysubjecting to evaporation under vacuum.

Step c):

The step c) of the aforementioned process involves reaction of thecompound of Formula V or a salt thereof; preferably free base, with acompound of Formula VI in presence of a coupling agent (C2), an additive(A2) and a base (B2) in a suitable solvent (S2) to obtain a compound ofFormula VII.

In a preferred embodiment, the present invention provides an improvedprocess for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof, comprising: reacting acompound of Formula V with a compound of Formula VI in presence of acoupling agent (C2), an additive (A2) and a base (B2) in a suitablesolvent (S2) to obtain a compound of Formula VII, wherein the couplingagent (C2) is used in an amount of about 0.9 to about 1.3 w/w moleequivalents per mole of Formula IV; wherein the additive (A2) is used incatalytic amount of about 0.05 to about 0.5 w/w mole equivalents permole of Formula IV.

In a preferred embodiment, the N-boc-L-homophenylalanine of Formula VIis having less than 0.1% of its corresponding D-isomer of Formula D:

The coupling agent (C2), an additive (A2), base (B2) and solvent (S2)are used herein for reaction of compound of Formula V with a compound ofFormula VI is same as used for step a) as mentioned above.

In a preferred embodiment, the coupling agent (C2) used herein isbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP) and is used in an amount of about 1.2 w/w mole equivalents permole of Formula IV; additive (A2) used herein is 1-Hydroxybenzotriazole(HOBt) and is used in an amount of about 0.1 w/w mole equivalents permole of Formula IV.

The reaction temperature should be sufficient to effect couplingreaction. Typically the reaction temperature is from about −10° C. toabout reflux temperature. Preferably the reaction temperature is about25° C. to about 50° C. The reaction may take from about 0.5 hours toabout 6 hours depending upon the coupling agent and additive, solventand temperature chosen, preferably about 1 hour to 4 hours.

After completion of the reaction, the compound of Formula VII isadvantageously isolated by quenching the step c) reaction mass in towater to precipitate compound of Formula IV as solid. The precipitatedcompound of Formula VII can be separated by methods known in the art,for example filtration.

The resultant product may optionally be dried using conventional methodsat a temperature ranging from about 40° C. to about 60° C. The compoundof Formula VII, obtained by the aforementioned process, have a chemicalpurity of at least about 95%, as measured by HPLC, preferably at leastabout 98%, as measured by HPLC and more preferably at least about 99.5%,as measured by HPLC; and contains less than 0.5% of total impurities,which include byproducts HOBt, PyBOP, tris(pyrrolidino phosphine) oxide,isomeric impurities of Formula 4, Formula 5, Formula 6 and Formula 7 asmeasured by HPLC; preferably less than 0.3%, as measured by HPLC.

In another embodiment, the obtained compound of Formula VII having lessthan 0.1%, as measured by HPLC of each of impurity of Formula 4, Formula5, Formula 6 or Formula 7; preferably less than 0.05%, as measured byHPLC; more preferably less than 0.03%, as measured by HPLC.

In another embodiment, the compound of Formula VII obtained by theprocess described above is in amorphous in nature.

In another embodiment, the present invention provides amorphous compoundof Formula VII characterized by a powder X-Ray diffraction (PXRD)pattern substantially in accordance with FIG. 2.

Step d):

The step d) of the aforementioned process involves deprotection ofbenzyl protecting group of the compound of Formula VII in presence of asuitable deprotecting agent to obtain a compound of Formula VIII.

The suitable deprotecting agent used herein for deprotection of thecompound of Formula VII is include, but is not limited to palladium oncarbon/ammonium formate, palladium on carbon/ammonium acetate, palladiumon carbon/hydrogen gas, palladium hydroxide/hydrogen gas, raneynickel/hydrogen gas, platinum oxide/hydrogen gas, zinc/hydrogen gas andthe like; preferably palladium on carbon/hydrogen gas.

The deprotection may be carried out in a suitable solvent, which includealcohols, esters, ethers, halogenated hydrocarbons, acetic acid, waterand mixtures thereof. The alcohols include, but are not limited tomethanol, ethanol, isopropanol and the like; esters include, but are notlimited to methyl acetate, ethyl acetate, propyl acetate, butyl acetateand the like; ethers include, but are not limited to tetrahydrofuran andthe like; halogenated hydrocarbons include, but are not limited tomethylene chloride, ethylene chloride and the like, and water andmixture thereof; preferably a mixture of methanol and methylenechloride.

The deprotection reaction may be carried out at a temperature of about0° C. to reflux temperature; preferably at 0° C. to about 50° C. Aftercompletion of the reaction, the reaction mass may be filtered andresulting compound of Formula VIII may be isolated by subjecting thefilterate to evaporation under vacuum to obtain a residue. Optionallythe obtained residue is treated with a suitable solvent such asn-heptane and stirred for about 2 hours and the resultant compound ofFormula VIII may be isolated by techniques known in the art, for examplefiltration.

Optionally resulting Formula VIII may be purified by dissolving in asuitable organic solvent such as ethyl acetate, methylene chloride,2-methyl tetrahydrofuran at a temperature of about 0° C. to refluxtemperature; preferably at 25° C. to about 50° C. The pure compound ofFormula VIII may be precipitated from the solution by either addition ofsuitable anti-solvent to the Formula VIII solution obtained as above,(or) addition of Formula VIII solution obtained as above into a suitableanti-solvent at a temperature of less than about 25° C. The suitableanti-solvent include, but are not limited to dimethyl ether, diethylether, diisopropyl ether, hexane, heptane, propane, cyclopropane,cyclobutane, cyclopentane, cyclohexane, methyl cyclohexane,cycloheptane, cyclooctane and the like and mixture thereof; preferablyFormula VIII is dissolved in ethyl acetate and precipitated by adding into antisolvent of heptane and the resultant compound of Formula VIII maybe isolated by techniques known in the art, for example filtration.

The resultant product may optionally be further dried by the knowntechniques at a temperature ranging from about 40° C. to about 60° C.The resulting Formula VIII, obtained by the aforementioned process, havea chemical purity of at least about 95%, as measured by HPLC, preferablyat least about 98%, as measured by HPLC and more preferably at leastabout 99.0%, as measured by HPLC; and having less than 0.1%, as measuredby HPLC of each of impurity of Formula 16, Formula 17, Formula 18 orFormula 19; preferably less than 0.05%, as measured by HPLC; morepreferably less than 0.03%, as measured by HPLC.

In another embodiment, the obtained compound of Formula VIII having lessthan 0.1%, as measured by HPLC of each of impurity of Formula 16,Formula 17, Formula 18 or Formula 19; preferably less than 0.05%, asmeasured by HPLC; more preferably less than 0.03%, as measured by HPLC.

In another embodiment, the compound of Formula VIII obtained by theprocess described above is in an amorphous nature.

In another embodiment, the present invention provides amorphous compoundof Formula VIII characterized by a powder X-Ray diffraction (PXRD)pattern substantially in accordance with FIG. 3.

Step e):

The step e) of the aforementioned process involves reaction of thecompound of Formula VIII with a compound of Formula IX or a salt threofin presence of a coupling agent (C3), an additive (A3) and a base (B3)in a suitable solvent (S3) to obtain a compound of Formula X.

In a preferred embodiment, the present invention provides an improvedprocess for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof, comprising: reacting acompound of Formula VIII with a compound of Formula IX or a salt threofin presence of a coupling agent (C3), an additive (A3) and a base (B3)in a suitable solvent (S3) to obtain a compound of Formula X; whereinthe coupling agent (C3) is used in an amount of about 0.9 to about 1.3w/w mole equivalents per mole of Formula VIII; wherein the additive (A3)is used in catalytic amount of about 0.05 to about 0.5 w/w moleequivalents per mole of Formula VIII.

In a preferred embodiment, the compound of Formula IX having less than0.1% of its corresponding isomers or its impurities of Formula E,Formula F, Formula G, Formula H, Formula I and Formula J:

The coupling agent (C3), an additive (A3), base (B3) and solvent (S3)are used herein for reaction of compound of Formula VIII with a compoundof Formula IX or a salt threof; preferably free base, is same as usedfor step a) as mentioned above.

In a preferred embodiment, the coupling agent (C3) used herein isbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP) and is used in an amount of about 1.2 w/w mole equivalents permole of Formula VIII; additive (A3) used herein is1-Hydroxybenzotriazole (HOBt) and is used in an amount of about 0.1 w/wmole equivalents per mole of Formula VIII.

The reaction temperature should be sufficient to effect couplingreaction. Typically the reaction temperature is from about −10° C. toabout reflux temperature. Preferably the reaction temperature is about25° C. to about 50° C. The reaction may take from about 0.5 hours toabout 6 hours depending upon the coupling agent and additive, solventand temperature chosen, preferably about 1 hour to 4 hours.

After completion of the reaction, the compound of Formula X isadvantageously isolated by quenching the step e) reaction mass in towater to precipitate compound of Formula X as solid. The precipitatedcompound of Formula X may be separated by methods known in the art, forexample filtration.

The present invention provides a compound of Formula X prepared by theprocess described as above having a purity of at least about 90%, asmeasured by HPLC, preferably at least about 95% as measured by HPLC, andmore preferably at least about 97.0%, as measured by HPLC; and containsless than 3% of total impurities, which includes byproducts of HOBt,PyBOP, tris(pyrrolidino phosphine) oxide; isomeric impurities of Formula20, Formula 21, Formula 22, Formula 23, Formula 24, Formula 25, Formula26 or Formula 27 as measured by HPLC.

In another embodiment, the compound of Formula X thus obtained may bepurified by treating the compound of Formula X in a suitable solvent.

In accordance with another embodiment, the present invention provides aprocess for purification of compound of Formula X, comprising:

-   -   a) dissolving compound of Formula X in one or more suitable        solvent at a temperature of about 30° C. to about reflux        temperature,    -   b) cooling the obtained solution to less than 10° C., and    -   c) filtering the compound of Formula X.

The one or more suitable solvent used herein for purification ofcompound of Formula X include but is not limited to alcohols, esters,ethers, nitriles, ketones, halogenated hydrocarbons and mixturesthereof. The alcohols include, but are not limited to methanol, ethanol,isopropanol, n-propanol, t-butanol and the like; esters include, but arenot limited to methyl acetate, ethyl acetate, isopropyl acetate and thelike; ethers include, but are not limited to tetrahydrofuran,2-methyltetrahydrofuran and the like; nitriles include, but are notlimited to acetonitrile, propionitrile and the like; ketones include,but are not limited to acetone, methyl ethyl ketone, methyl isobutylketone and the like; halogenated hydrocarbons include, but are notlimited to methylene chloride and the like and mixtures thereof;preferably ethyl acetate.

The solution may be heated to dissolve the compound of Formula X. Thetemperature suitable for dissolving compound of Formula X depends on thesolvent used and the amount of compound of Formula X in the solution.Typically, the solution is heated at a temperature of at least about 30°C. to about reflux; preferably at 50° C. to about 80° C. The resultantreaction solution may be cooled at a temperature from about 10° C. orless such that the compound of Formula X can be isolated by conventionaltechniques, for example filtration.

The present invention provides a compound of Formula X prepared by thepurification as described above having a purity of at least about 97%,as measured by HPLC, preferably at least about 98% as measured by HPLC,and more preferably at least about 99.5%, as measured by HPLC; andcontains less than 0.5% of total impurities, which include byproducts ofHOBt, PyBOP, tris(pyrrolidino phosphine) oxide; isomeric impurities ofFormula 20, Formula 21, Formula 22, Formula 23, Formula 24, Formula 25,Formula 26 or Formula 27 as measured by HPLC; preferably less than 0.3%,as measured by HPLC.

In another embodiment, the obtained compound of Formula X having lessthan 0.1%, as measured by HPLC of each of impurity of Formula 20,Formula 21, Formula 22, Formula 23, Formula 24, Formula 25, Formula 26or Formula 27; preferably less than 0.05%, as measured by HPLC; morepreferably less than 0.03%, as measured by HPLC.

Step f):

The step f) of the aforementioned process involves deprotection of amineprotecting group of Formula X with a suitable acid to obtain a compoundof Formula XI or a salt thereof is may be carried out in a suitableorganic solvent.

The suitable acid and suitable organic solvent are used herein fordeprotection of amine protecting group of Formula X is same as used forstep b) as mentioned above.

The deprotection reaction may be carried out at a temperature of about0° C. to reflux temperature; preferably at 0° C. to about 50° C. Aftercompletion of the reaction, the reaction mass may be basified with asuitable aqueous base such as sodium carbonate, potassium carbonate andthe like and then extracting the product with water immiscible organicsolvent such as ethyl acetate, methylene chloride and the like. The freebase of compound of Formula XI may be isolated from the resultant waterimmiscible organic solvent by subjecting to evaporation under vacuum; orthe reaction mass may be isolated as solid compound preferably bydirectly evaporating the acid salt of compound of Formula XI containingreaction solution to obtain solid acid salt of compound of Formula XI.

In a preferred embodiment, the compound of Formula XI is isolated astrifluoro acetic salt and is in an amorphous in nature.

In another embodiment, the present invention provides amorphous Form oftrifluoro acetic acid salt of Formula XI.

In another embodiment, the present invention provides amorphous Form oftrifluoro acetic acid salt of Formula XI characterized by a powder X-Raydiffraction (PXRD) pattern substantially in accordance with FIG. 5.

In a preferred embodiment, the compound of Formula XI is isolated as itsfree base and is in amorphous in nature.

In another embodiment, the present invention provides amorphous form ofFormula XI free amine.

In another embodiment, the present invention provides amorphous Form ofFormula XI free amine characterized by a powder X-Ray diffraction (PXRD)pattern substantially in accordance with FIG. 6.

Step g):

The step g) of the aforementioned process involves reaction of compoundof Formula XI or a salt thereof with a compound of Formula XII or a saltthereof in presence of a coupling agent (C4), an additive (A4) and abase (B4) in a suitable solvent (S4) to obtain carfilzomib of Formula I.

In a preferred embodiment, the present invention provides an improvedprocess for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof, comprising: reacting acompound of Formula XI or a salt thereof with a compound of Formula XIIor a salt threof in presence of a coupling agent (C4), an additive (A4)and a base (B4) in a suitable solvent (S4) to obtain carfilzomib or apharmaceutically acceptable salt thereof; wherein the coupling agent(C4) is used in an amount of about 0.9 to about 1.3 w/w mole equivalentsper mole of Formula X; wherein the additive (A4) is used in catalyticamount of about 0.05 to about 0.5 w/w mole equivalents per mole ofFormula X.

The coupling agent (C4), an additive (A4), base (B4) and solvent (S4)are used herein for reaction of compound of Formula XI or a saltthereof, preferably free base with a compound of Formula XII or a saltthreof; preferably hydrochloride salt, is same as used for step a) asmentioned above.

In a preferred embodiment, the coupling agent (C4) used herein isbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP) and is used in an amount of about 1.2 w/w mole equivalents permole of Formula X; additive (A4) used herein is 1-Hydroxybenzotriazole(HOBt) and is used in an amount of about 0.1 w/w mole equivalents permole of Formula X.

The reaction temperature should be sufficient to effect couplingreaction. Typically the reaction temperature may be from about −10° C.to about reflux temperature. Preferably the reaction temperature isabout 25° C. to about 50° C. The reaction may take from about 0.5 hoursto about 6 hours depending upon the coupling agent and additive, solventand temperature chosen, preferably about 1 hour to 4 hours.

After completion of the reaction, the carfilzomib of Formula I isisolated by quenching the step g) reaction mass in to water toprecipitate carfilzomib as solid. The precipitated carfilzomib ofFormula I may be separated by methods known in the art, for examplefiltration.

The present invention provides carfilzomib prepared by the processdescribed as above having a purity of at least about 98%, as measured byHPLC, preferably at least about 99% as measured by HPLC.

Alternatively, the resultant carfilzomib of Formula I can be convertedin to its pharmaceutically acceptable salt thereof.

The present inventors have surprisingly found that, isolation ofcarfilzomib as its pharmaceutically acceptable salt thereof enhancespurity by removing the impurities formed during the preparation andisomer impurities, if any.

In another embodiment, the present invention provides a process forpurification of carfilzomib, comprising:

-   -   a) providing a solution of carfilzomib in one or more organic        solvents,    -   b) adding maleic acid to the step a) solution,    -   c) isolating the carfilzomib maleic acid salt,    -   d) neutralizing the carfilzomib maleic acid salt in a suitable        solvent using a base,    -   e) concentrating the step d) solution under vacuum to obtain a        residue,    -   f) dissolving the step e) residue in a suitable solvent,    -   g) adding the step f) solution to an anti-solvent, or        vice-versa, and    -   h) isolating the pure carfilzomib.

The one or more organic solvents for providing a solution of carfilzomibinclude, but are not limited to alcohols, esters, ethers, nitriles,halogenated solvents and mixtures thereof. The alcohols includes, butare not limited to methanol, ethanol, isopropanol and the like; esterssuch as methyl acetate, ethyl acetate, isopropyl acetate and the like;ethers such as tetrahydrofuran, methyl tertiary butyl ether and thelike; nitriles such as acetonitrile, propionitrile and the like;halogenated solvents such as methylene chloride, chloroform and the likeand mixture thereof; preferable a mixture of acetonitrile andtetrahydrofuran.

The suitable temperature for dissolving carfilzomib includes atemperature of about 25° C. to reflux; preferably at about 25° C. toabout 35° C.

Then the crystalline carfilzomib maleate salt can be recovered by anyconventional techniques known in the art, for example filtration.Typically, if stirring is involved, the temperature during stirring canrange from about 25° C. to about 35° C. and the resultant product mayoptionally be further dried. Drying can be suitably carried out in atray dryer, vacuum oven, air oven and the like. The drying can becarried out at a temperature ranging from about 40° C. to about 60° C. Ahigh purity level of the resulting carfilzomib, obtained by theaforementioned process, may have a chemical purity of at least about98%, as measured by HPLC, preferably at least about 99%, as measured byHPLC and more preferably at least about 99.9%, as measured by HPLC andcontains less than 0.1%, as measured by HPLC of each of impurity ofFormula 28, Formula 29, Formula 30, Formula 31, Formula 32, Formula 33,Formula 34, Formula 35, Formula 36, Formula 37, Formula 38, Formula 39,Formula 40 or Formula 41; preferably less than 0.05%, as measured byHPLC; more preferably less than 0.03%, as measured by HPLC.

The step of neutralizing the carfilzomib maleic acid salt involvestreating the carfilzomib maleic acid salt with a suitable base, where inthe base includes but are not limited to sodium carbonate, potassiumcarbonate, sodium bicarbonate, potassium bicarbonate, ammonium hydroxideand mixtures thereof; preferably sodium bicarbonate.

The step of neutralizing the carfilzomib maleic acid salt may be carriedout in a suitable solvent. The suitable solvent includes but is notlimited to esters, halogenated solvents, aromatic hydrocarbons andmixtures thereof. The esters such as methyl acetate, ethyl acetate,isopropyl acetate and the like; halogenated solvents such as methylenechloride, chloroform and the like; aromatic hydrocarbons include, butare not limited to toluene, xylene and the like, water and mixturethereof; preferable methylene chloride, water or mixtures thereof.

Then the product containing organic layer may be separated and followedby concentrating under vacuum at a temperature of about 25° C. to about65° C.; preferably at about 30° C. to about 45° C. to obtain carfilzomibas a residue.

The residue so obtained is dissolved in a suitable solvent to obtain asolution at a suitable temperature. Typically, the solution is heated ata temperature of at least about 30° C. to about reflux temperature,wherein the suitable solvent includes, but are not limited to alcoholssuch as methanol, ethanol, isopropanol, n-propanol, n-butanol, t-butanoland the like and mixtures thereof preferably methanol. The carfilzomibmay be precipitated by adding the step f) solution to an anti-solvent ofwater at a temperature of about 0° C. to about 35° C.; preferably atless than 10° C.

The carfilzomib can be recovered by any conventional techniques known inthe art, for example filtration. Typically, if stirring is involved, thetemperature during stirring can range from about 0° C. to about 30° C.,preferably at less than 10° C. and the resultant product may optionallybe further dried. Drying can be suitably carried out in a tray dryer,vacuum oven, air oven and the like. The drying can be carried out at atemperature ranging from about 35° C. to about 60° C. A high puritylevel of the resulting amorphous carfilzomib, obtained by theaforementioned process, may have a chemical purity of at least about98%, as measured by HPLC, preferably at least about 99%, as measured byHPLC and more preferably at least about 99.9%, as measured by HPLC andcontains less than 0.1%, as measured by HPLC of each of impurity ofFormula 28, Formula 29, Formula 30, Formula 31, Formula 32, Formula 33,Formula 34, Formula 35, Formula 36, Formula 37, Formula 38, Formula 39,Formula 40 or Formula 41; preferably less than 0.05%, as measured byHPLC; more preferably less than 0.03%, as measured by HPLC.

Carfilzomib recovered using the purification process of the presentinvention is in substantially amorphous form.

In another embodiment, the present invention provides carfilzomibobtained by the aforementioned process, containing less than 0.05% asmeasured by HPLC of one or more of impurities of Formula 1 to Formula41; preferably 0.03% as measured by HPLC.

In another embodiment, the present invention provides carfilzomibmaleate salt.

In another embodiment, the present invention provides crystallinecarfilzomib maleate salt.

In another embodiment, the present invention provides crystallinecarfilzomib maleate salt characterized by a powder X-Ray diffraction(PXRD) pattern substantially in accordance with FIG. 7.

In another embodiment, the present invention provides a process forpreparation of amorphous Form of carfilzomib, comprising:

-   -   a) providing a solution of carfilzomib pharmaceutically        acceptable salt in a suitable solvent,    -   b) neutralizing the step a) solution with a base,    -   c) concentrating the step b) solution under vacuum to obtain a        residue,    -   d) dissolving the step c) residue in a suitable solvent,    -   e) adding the step d) solution to an anti-solvent, or        vice-versa, and    -   f) isolating the amorphous form of carfilzomib.

Any form of carfilzomib salt or a solution of carfilzomib salt obtainedfrom previous processing steps can be used as starting material in theprocess of making the amorphous carfilzomib of the present invention.

The carfilzomib salt used to prepare carfilzomib amorphous form is anysalt of carfilzomib; preferably maleate salt of carfilzomib.

The step a) process involves providing a solution of maleate salt ofcarfilzomib in a suitable solvent at a temperature of about 25° C. toabout 35° C. The suitable solvent of step a) includes, but is notlimited to esters, halogenated solvents, aromatic hydrocarbons, waterand mixtures thereof. The esters such as methyl acetate, ethyl acetate,isopropyl acetate and the like; halogenated solvents such as methylenechloride, chloroform and the like; aromatic hydrocarbons include, butare not limited to toluene, xylene and the like mixtures thereof andmixture thereof preferable methylene chloride, water and mixturethereof.

The step b) process involves neutralizing the step a) solution with abase, where in the base includes but are not limited to sodiumcarbonate, potassium carbonate, sodium bicarbonate, potassiumbicarbonate, ammonium hydroxide and mixtures thereof; preferably sodiumbicarbonate.

Then the product containing organic layer may be separated and followedby concentrating under vacuum at a temperature of about 25° C. to about65°; preferably at about 30° C. to about 45° C. to obtain carfilzomib asa residue.

The residue so obtained is dissolved in a suitable solvent to obtain asolution at a suitable temperature. Typically, the solution is heated ata temperature of at least about 30° C. to about reflux temperature,wherein the suitable solvent includes, but are not limited to methanol,ethanol, isopropanol, n-propanol, n-butanol, t-butanol and the like andmixtures thereof; preferably methanol. The carfilzomib amorphous Formmay be precipitated by adding the step d) solution to an anti-solvent ofwater at a temperature of about 0° C. to about 35°; preferably at lessthan 10° C.

The carfilzomib amorphous Form can be recovered by any conventionaltechniques known in the art, for example filtration. Typically, ifstirring is involved, the temperature during stirring can range fromabout 0° C. to about 30° C., preferably at less than 10° C. and theresultant product may optionally be further dried. Drying can besuitably carried out in a tray dryer, vacuum oven, air oven and thelike. The drying can be carried out at a temperature ranging from about35° C. to about 60° C. A high purity level of the resulting amorphouscarfilzomib, obtained by the aforementioned process, may have a chemicalpurity of at least about 98%, as measured by HPLC, preferably at leastabout 99%, as measured by HPLC and more preferably at least about 99.9%,as measured by HPLC and contains less than 0.1%, as measured by HPLC ofeach of impurity of Formula 28, Formula 29, Formula 30, Formula 31,Formula 32, Formula 33, Formula 34, Formula 35, Formula 36, Formula 37,Formula 38, Formula 39, Formula 40 or Formula 41; preferably less than0.05%, as measured by HPLC; more preferably less than 0.03%, as measuredby HPLC.

In another embodiment, the present invention provides carfilzomibobtained by the aforementioned process, containing less than 0.05% asmeasured by HPLC of one or more of impurities of Formula 1 to Formula41; preferably 0.03% as measured by HPLC.

In another embodiment, the present invention provides an improvedprocess for the preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof:

comprising:

-   -   a1) reacting a compound of Formula II with a compound of Formula        III or a salt thereof in presence of a coupling agent (C1), an        additive (A1) and a base (B1) in a suitable solvent (S1) to        obtain a compound of Formula IV,

-   -   b1) reacting the compound of Formula IV with a suitable acid to        obtain a compound of Formula V or a salt thereof,

-   -   c1) reacting the compound of Formula V or a salt thereof with a        compound of Formula VI in presence of a coupling agent (C2), an        additive (A2) and a base (B2) in a suitable solvent (S2) to        obtain a compound of Formula VII,

-   -   d1) reacting the compound of Formula VII with a suitable acid to        obtain a compound of Formula XIII or a salt thereof,

-   -   e1) reacting the compound of Formula XIII or a salt thereof with        a compound of Formula XII in presence of a coupling agent (C5),        an additive (A5) and a base (B5) in a suitable solvent (S5) to        obtain a compound of Formula XIV,

-   -   f1) deprotecting the compound of Formula XIV in presence of a        suitable deprotecting agent to obtain a compound of Formula XV,        and

-   -   g1) reacting the compound of Formula XV with a compound of        Formula IX or a salt threof in presence of a coupling agent        (C6), an additive (A6) and a base (B6) in a suitable solvent        (S6) to obtain carfilzomib or a pharmaceutically acceptable salt        thereof,

wherein the coupling agent (C1), (C2), (C5) and (C6) are used in anamount of about 0.9 to about 1.3 w/w mole equivalents per mole ofFormula III, Formula IV, Formula VII and Formula XV respectively;wherein the additive (A1), (A2), (A3) and (A4) are used in catalyticamount of about 0.05 to about 0.5 w/w mole equivalents per mole ofFormula III, Formula IV, Formula VII and Formula XV respectively.

The compound of Formula II, L-phenyl alanine benzyl ester of Formula IIIor a salt thereof, N-boc-homophenylalanine of Formula VI and morpholineacetic acid of Formula XII are known in the art and can be procured fromcommercially available sources.

The suitable salt of compounds of Formula III, Formula V or Formula IXemployed in the aforementioned process is a salt of a mineral or organicacid, such as HCl, HBr, HI, HNO₃, H₂SO₄, acetic acid, trifluoro aceticacid, formic acid and the like.

The aforementioned process of step a1), step b2) and step c3) ofconverting compound of Formula II to compound of Formula VII can becarried out by the process described as above in the presentspecification.

Step d1):

The step d1) of the aforementioned process involves deprotection ofamine protecting group of Formula VII with a suitable acid to obtain acompound of Formula XIII or a salt thereof.

The suitable acid used herein for step d1) is selected from the groupconsisting of hydrochloric acid, hydrobromic acid, sulfuric acid,phosphoric acid, acetic acid, trifluoro acetic acid, trichloro aceticacid, methane sulfonic acid and the like and mixture thereof; preferablytrifluoro acetic acid.

The deprotection reaction of compound of Formula VII with a suitableacid may be carried out in a suitable organic solvent. The suitableorganic solvent includes but is not limited to alcohols, ketones,ethers, halogenated hydrocarbons and mixtures thereof. The alcoholsinclude, but are not limited to methanol, ethanol, isopropanol and thelike; ketones include, but are not limited to acetone, methyl isobutylketone, methyl ethyl ketone and the like; ethers include, but are notlimited to tetrahydrofuran, dimethyl ether, diisopropyl ether, methyltertiary butyl ether, 1,4-dioxane and the like; halogenated hydrocarbonsinclude, but are not limited to methylene chloride, ethylene chlorideand the like and mixture thereof preferably methylene chloride.

The deprotection reaction may be carried out at a temperature of about0° C. to reflux temperature; preferably at 0° C. to about 50° C. Aftercompletion of the reaction, the reaction mass may be basified with asuitable aqueous base such as sodium carbonate, potassium carbonate andthe like and then extracting the product with water immiscible organicsolvent such as ethyl acetate, methylene chloride and the like. The freebase of compound of Formula XIII may be isolated from the resultantwater immiscible organic solvent by subjecting to evaporation undervacuum.

Step e1):

The step e1) of the aforementioned process involves reaction of thecompound of Formula XIII or a salt thereof with a compound of FormulaXII in presence of a coupling agent (C5), an additive (A5) and a base(B5) in a suitable solvent (S5) to obtain a compound of Formula XIV.

In a preferred embodiment, the present invention provides an improvedprocess for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof, comprising: reacting acompound of Formula XIII or a salt thereof; preferably free base, with acompound of Formula XII in presence of a coupling agent (C5), anadditive (A5) and a base (B5) in a suitable solvent (S5) to obtain acompound of Formula XIV, wherein the coupling agent (C5) is used in anamount of about 0.9 to about 1.3 w/w mole equivalents per mole ofFormula VII; wherein the additive (A5) is used in catalytic amount ofabout 0.05 to about 0.5 w/w mole equivalents per mole of Formula VII.

The coupling agent (C5) used herein for reaction of compound of FormulaXIII or a salt thereof; preferably free base with a compound of FormulaXII is selected from the group consisting ofbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP), benzotriazol-1-yloxy-tris (dim ethyl amino)-phosphoniumhexafluorophosphate (BOP), bromo-tripyrrolidino-phosphoniumhexafluorophosphate (PyBrOP), Propylphosphonic anhydride (T3P),N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC),1,1′-Carbonyldiimidazole (CDI), diisopropylcarbodiimide (DCI),dicyclohexyl carbodiimide (DCC) and the like and mixture thereof;preferably benzotriazol-1-yl-oxytripyrrolidinophosphoniumhexafluorophosphate (PyBOP).

The additive (A5) used herein for reaction of compound of Formula XIIIor a salt thereof; preferably free base with a compound of Formula XIIis selected from the group consisting of 1-Hydroxybenzotriazole (HOBt),1-Hydroxy-7-aza-1H-benzotriazole (HOAt),2-(1H-Benzotriazol-1-yl)-N,N,N′,N′-tetramethylaminiumtetrafluoroborate/hexa fluoro phosphate (TBTU),2-(7-Aza-1H-benzotriazol-1-yl)-N,N,N′,N′-tetramethylaminiumhexafluorophosphate) (HATU) and the like and mixture thereof; preferablyis 1-Hydroxybenzotriazole (HOBt).

In a preferred embodiment, the coupling agent (C5) used herein isbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP) and is used in an amount of about 1.2 w/w mole equivalentsFormula VII; additive (A5) used herein is 1-Hydroxybenzotriazole (HOBt)and is used in an amount of about 0.1 w/w mole equivalents per mole ofFormula VII.

Exemplary bases (B5) used herein for reaction of compound of FormulaXIII or a salt thereof; preferably free base with a compound of FormulaXII includes but are not limited to diisopropylethyl amine, Imidazole orits salts, 1,8-Diazabicyclo[5.4.0]undec-7-en (DBU), tertiary amines orits hydro halide salts thereof selected from the group consisting oftriethyl amine-hydrochloride and the like and mixtures thereof;preferably diisopropylethyl amine.

The reaction of compound of Formula XIII or a salt thereof; preferablyfree base with a compound of Formula XII is advantageously carried outin a solvent (S5). Suitable solvent include, but are not limited toethers, esters, halogenated hydrocarbons, amides, aromatic solvents,nitriles, or mixtures thereof. The ether includes, but are not limitedto tetrahydrofuran, 2-methyltetrahydrofuran and the like; estersinclude, but are not limited to methyl acetate, ethyl acetate, propylacetate, butyl acetate and the like; halogenated hydrocarbons include,but are not limited to methylene chloride, ethylene chloride and thelike; amides includes, but are not limited to dimethyl formamide,dimethyl acetamide, N-methyl pyrrolidinone and the like; aromaticsolvents include, but are not limited to toluene, chlorobenzene and thelike; nitriles include, but are not limited to acetonitrile,propionitrile and the like and mixtures thereof; preferably dimethylformamide and acetonitrile.

The reaction temperature should be sufficient to effect couplingreaction. Typically the reaction temperature may be from about −10° C.to about reflux temperature. Preferably the reaction temperature isabout 25° C. to about 50° C. The reaction may take from about 0.5 hoursto about 6 hours depending upon the coupling agent and additive, solventand temperature chosen, preferably about 1 hour to 4 hours.

After completion of the reaction, the compound of Formula XIV isadvantageously isolated by quenching the step e1) reaction mass in towater to precipitate compound of Formula XIV as solid. The precipitatedcompound of Formula XIV may be separated by methods known in the art,for example filtration.

The resultant product may optionally be further dried. Drying can besuitably carried out in a tray dryer, vacuum oven, air oven and thelike. The drying can be carried out at a temperature ranging from about40° C. to about 60° C. A high purity level of the resulting Formula XIV,obtained by the aforementioned process, may have a chemical purity of atleast about 95%, as measured by HPLC, preferably at least about 98%, asmeasured by HPLC and more preferably at least about 99.0%, as measuredby HPLC; and contains less than 0.5% of total impurities of byproductsHOBt, PyBOP, tris(pyrrolidino phosphine) oxide, isomer impurities ofFormula 8, Formula 9, Formula 10 and Formula 11, as measured by HPLC;preferably less than 0.3%, as measured by HPLC.

In another embodiment, the obtained compound of Formula XIV having lessthan 0.1%, as measured by HPLC of each of impurity of Formula 8, Formula9, Formula 10 or Formula 11; preferably less than 0.05%, as measured byHPLC; more preferably less than 0.03%, as measured by HPLC.

Step f1):

The step f1) of the aforementioned process involves deprotection ofbenzyl protecting group of the compound of Formula XIV in presence of asuitable deprotecting agent to obtain a compound of Formula XV.

The suitable deprotecting agent used herein for deprotection of thecompound of Formula XV is include, but is not limited to palladium oncarbon/ammonium formate, palladium on carbon/ammonium acetate, palladiumon carbon/hydrogen gas, palladium hydroxide/hydrogen gas, raneynickel/hydrogen gas, platinum oxide/hydrogen gas, zinc/hydrogen gas andthe like; preferably palladium on carbon/ammonium formate.

The deprotection reaction of compound of Formula XIV with a suitabledeprotecting agent may be carried out in a suitable solvent. Thesuitable solvent includes but is not limited to alcohols, esters,ethers, acetic acid, water and mixtures thereof. The alcohols include,but are not limited to methanol, ethanol, isopropanol and the like;esters include, but are not limited to methyl acetate, ethyl acetate,propyl acetate, butyl acetate and the like; ethers include, but are notlimited to tetrahydrofuran and the like; water and mixture thereof;preferably methanol.

The deprotection reaction may be carried out at a temperature of about0° C. to reflux temperature; preferably at 0° C. to about 50° C. Aftercompletion of the reaction, the reaction mass may be filtered andresulting compound of Formula XV may be isolated by subjecting thefilterate to evaporation under vacuum to obtain a residue. Optionallythe obtained residue is treated with a suitable solvent such as acetoneand stirred for about 2 hours and the resultant compound of Formula XVmay be isolated by techniques known in the art, for example filtration.

The resultant product may optionally be further dried. Drying can besuitably carried out in a tray dryer, vacuum oven, air oven and thelike. The drying can be carried out at a temperature ranging from about40° C. to about 60° C. A high purity level of the resulting Formula XV,obtained by the aforementioned process, may have a chemical purity of atleast about 95%, as measured by HPLC, preferably at least about 98%, asmeasured by HPLC and more preferably at least about 99.5%, as measuredby HPLC; and contains less than 0.5% of total impurities of Formula 12,Formula 13, Formula 14 and Formula 15 as measured by HPLC; preferablyless than 0.3%, as measured by HPLC.

In another embodiment, the obtained compound of Formula XV having lessthan 0.1%, as measured by HPLC of each of impurity of Formula 12,Formula 13, Formula 14 or Formula 15; preferably less than 0.05%, asmeasured by HPLC; more preferably less than 0.03%, as measured by HPLC.

Step g1):

The step g1) of the aforementioned process involves reaction of thecompound of Formula XV with a compound of Formula IX or a salt threof inpresence of a coupling agent (C6), an additive (A6) and a base (B6) in asuitable solvent (S6) to obtain carfilzomib of Formula I.

In a preferred embodiment, the present invention provides an improvedprocess for preparation of carfilzomib of Formula I or apharmaceutically acceptable salt thereof, comprising: reacting acompound of Formula XV with a compound of Formula IX or a salt threof inpresence of a coupling agent (C6), an additive (A6) and a base (B6) in asuitable solvent (S6) to obtain carfilzomib or a pharmaceuticallyacceptable salt thereof; wherein the coupling agent (C6) is used in anamount of about 0.9 to about 1.3 w/w mole equivalents per mole ofFormula XV; wherein the additive (A6) is used in catalytic amount ofabout 0.05 to about 0.5 w/w mole equivalents per mole of Formula XV.

In a preferred embodiment, the compound of Formula IX is having lessthan 0.1% of its corresponding isomers or its impurities of Formula E,Formula F, Formula G, Formula H, Formula I and Formula J:

The coupling agent (C6), an additive (A6), base (B6) and solvent (S6)are used herein for reaction of compound of Formula XV with a compoundof Formula IX or a salt threof, preferably free base is same as used forstep e1) as mentioned above.

In a preferred embodiment, the coupling agent (C6) used herein isbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP) and is used in an amount of about 1.2 w/w mole equivalents permole of Formula XV; additive (A6) used herein is 1-Hydroxybenzotriazole(HOBt) and is used in an amount of about 0.1 w/w mole equivalents permole of Formula XV.

The reaction temperature should be sufficient to effect couplingreaction. Typically the reaction temperature may be from about −10° C.to about reflux temperature. Preferably the reaction temperature isabout 25° C. to about 50° C. The reaction may take from about 0.5 hoursto about 6 hours depending upon the coupling agent and additive, solventand temperature chosen, preferably about 1 hour to 4 hours.

After completion of the reaction, the obtained carfilzomib may beisolated by subjecting the reaction mass to evaporation under vacuum toobtain a residue.

Alternatively, the resultant residue of carfilzomib can be converted into its pharmaceutically acceptable salt thereof; preferably maleate saltby using the process described as above in the present specification.

In another embodiment, the present invention provides the conversion ofcarfilzomib pharmaceutically acceptable salt in to its free base ofcarfilzomib amorphous form by using the process described as above inthe present specification.

A high purity level of the resulting amorphous carfilzomib, obtained bythe aforementioned process, may have a chemical purity of at least about98%, as measured by HPLC, preferably at least about 99%, as measured byHPLC and more preferably at least about 99.9%, as measured by HPLC andcontains less than 0.1%, as measured by HPLC of each of impurity ofFormula 28, Formula 29, Formula 30, Formula 31, Formula 32, Formula 33,Formula 34, Formula 35, Formula 36, Formula 37, Formula 38, Formula 39,Formula 40 or Formula 41; preferably less than 0.05%, as measured byHPLC; more preferably less than 0.03%, as measured by HPLC.

In another embodiment, the present invention provides carfilzomibobtained by the aforementioned process, containing less than 0.05% asmeasured by HPLC of one or more of impurities of Formula 1 to Formula41; preferably 0.03% as measured by HPLC.

In another embodiment, the present invention provides a compound ofFormula 41:

In another embodiment, the present invention provides a compound ofFormula 41 characterized by ¹H-NMR (DMSO-d6): δ 0.80 (m, 6H), 0.83 (m,6H), 0.83 (m, 6H), 0.85 (m, 6H), 0.87 (m, 3H), 1.11 (S, 3H), 1.24 (m,1H), 1.32 (m, 2H), 1.36 (m, 3H), 1.36 (m, 2H), 1.4 (S, 3H), 1.53 (m,1H), 1.53 (m, 1H), 1.60 (m, 2H), 1.63 (m, 1H), 1.63 (m, 1H), 1.66 (m,1H), 1.84 (m, 2H), 2.38 (m, 1H), 2.45 (m, 4H), 2.5 (m, 2H), 2.63 (m,1H), 2.75 (m, 1H), 2.75 (m, 1H), 2.9 (m, 1H), 2.95 (m, 1H), 2.96 (m,1H), 2.96 (m, 2H), 3.12 (d, 1H), 3.6 (m, 4H), 4.32 (m, 1H), 4.32 (m,1H), 4.35 (m, 1H), 4.36 (m, 1H), 4.54 (m, 1H), 4.54 (m, 1H), 5.1 (t,1H), 5.4 (s, 1H), 7.09-7.18 (m, 10H), 7.11-7.26 (m, 10H), 7.88 (d, 1H),8.04 (m, 1H), 8.09 (m, 1H), 8.11 (m, 1H), 8.29 (d, 1H).

The repetition of '818 patent, which involves all the coupling reactionswith excess quantity of coupling agent, an additive and solvent resultsless percentage of product yields in all stages when compared to thetheoretical yields. In contrast the present invention involve use ofless quantity of coupling agents, an additives and solvents for thepreparation of carfilzomib, which observes less reaction time withhigher product convertion there by process results higher yields andpurity.

A comparative step wise results of US'818 patent process and the presentaforementioned process are reported in the following table:

Purity Reported Theoretical Reagents by Yield yield Step Process (moleeqt) Solvent HPLC (w/w %) (w/w %) Reaction of US′818 PyBOP Acetonitrile88.12%   1%  1.6% Formula II process (1.6); (45 vol) with HOBt (1.6)Formula III Present PyBOP DMF 99.53% 1.4% process (1.2); (5 vol) HOBt(0.1) Reaction of US′818 PyBOP Acetonitrile 89.35% 0.99%  1.35% FormulaV process (1.6); (22 vol) with HOBt (1.6) Formula VI Present PyBOP DMF 97.1% 1.2% process (1.2); (5vol) HOBt (0.1) Reaction of US′818 PyBOPDMF  92.1% 0.6% 1.04% Formula process (1.6); (24 vol) XIII with HOBt(1.6) Formula XII Present PyBOP DMF  97.6% 0.95%  process (1.2); (5 vol)HOBt (0.1) Reaction of US′818 PyBOP Acetonitrile   26% 0.8% 1.27%Formula XV process (1.6); (50 vol) (isolated as with HOBt (1.6)amorphous) Formula IX Present PyBOP Acetonitrile   99% 1% (isolatedprocess (1.2); (50 vol) as maleate HOBt (0.1) salt)

In another embodiment, the present invention provides a process forpreparation of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI,

comprising:

-   -   i) reacting a compound of Formula XVII with alkyl magnesium        halide to obtain a compound of Formula XVIII,    -   ii) crystallizing the compound of Formula XVIII from a suitable        solvent system to obtain crystalline compound of Formula XVIII,

-   -   iii) reducing the crystalline compound of Formula XVIII in        presence of a suitable reducing agent to obtain a diastereomeric        mixture of compound of Formula XIXa and Formula XIXb,    -   iv) crystallizing the mixture of compound of Formula XIXa and        Formula XIXb from a suitable solvent system to obtain a mixture        of crystalline compound of Formula XIXa and Formula XIXb,

-   -   v) epoxidation and followed by oxidation of diastereomeric        mixture of crystalline compound of Formula XIXa and Formula XIXb        to obtain a diastereomeric mixture of compound of Formula XVI        and Formula XVIa,

-   -   vi) separating the compound of Formula XVI from the        diastereomeric mixture of compound of Formula XVI and Formula        XVIa by chromatography, and    -   vii) crystallizing the compound of Formula XVI from a suitable        solvent system to obtain crystalline compound of Formula XVI.

The starting material of Formula XVII is known in the art and can beprepared by any known method, for example WO2009/045467 or may be byprepared by the process described in example part.

Step i) of reaction of compound of Formula XVII with alkyl magnesiumhalide such as iso-propenyl magnesium bromide is carried out in asuitable organic solvent, which includes but is not limited to esters,ketones, ethers and mixtures thereof. The esters include, but are notlimited to ethyl acetate, isopropyl acetate and the like; ketonesinclude, but are not limited to acetone, methyl isobutyl ketone, methylethyl ketone and the like; ethers include, but are not limited totetrahydrofuran, dimethyl ether, diisopropyl ether, methyl tertiarybutyl ether, 1,4-dioxane and the like and mixtures thereof preferablytetrahydrofuran.

The reaction of compound of Formula XVII with iso-propenyl magnesiumbromide is carried out at a temperature of about 25° C. to about refluxtemperature; preferably at about 25° C. to about 50° C.

After completion of the reaction, the reaction mass may be quenched intoammonium chloride solution and compound of Formula XVIII may beextracted with water immiscible organic solvent such as ethyl acetate,methylene chloride, methyl tertiary butyl ether; preferable ethylacetate and distilling out the water immiscible organic solvent undervacuum to obtain a compound of Formula XVIII as residue. The obtainedresidue may be purified by column chromatography using ethyl acetate andcyclohexane as an eluent system and the compound containing solventfractions are combined and distilled under vacuum to obtain a compoundof Formula XVIII as residue. The residue obtained is purified by asolvent crystallization method to isolating the compound of FormulaXVIII as a crystalline solid.

In an embodiment, the compound of Formula XVIII may be purified byrecrystallization to obtain compound of Formula XVIII as a crystallinesolid.

In another embodiment, the present invention provides a process for thepreparation of compound of Formula XVIII as crystalline solid,comprising:

-   -   i) providing a solution of compound of Formula XVIII in a        suitable solvent,    -   ii) optionally cooling the step i) solution to less than 20° C.,    -   iii) adding an anti-solvent to the step ii) solution, and    -   iv) isolating the crystalline compound of Formula XVIII; wherein        the suitable solvent is selected from the group comprising        alcohols, ketones, esters, nitriles and the like and mixture        thereof; and the anti-solvent is selected from the group        comprising aliphatic hydrocarbons, cyclic hydrocarbons, ethers        and the like and water and mixture thereof.

The step i) of providing a solution of Formula XVIII includes heating todissolve the compound of Formula XVIII obtained by the process describedabove in a suitable solvent at a temperature of about 25° C. to aboutreflux temperature; preferably at about 25° C. to about 35° C.

The suitable solvent for dissolving compound of Formula XVIII include,but is not limited to alcohols, ketones, esters, nitriles and the likeand mixture thereof. The alcohols include, but are not limited tomethanol, ethanol, propanol, isopropanol and the like; ketones include,but are not limited to acetone, methyl isobutyl ketone, methyl ethylketone and the like; esters include, but are not limited to methylacetate, ethyl acetate, isopropyl acetate and the like; nitrilesinclude, but are not limited to acetonitrile, propionitrile and the likeand mixture thereof preferably acetone. The optional step of cooling thestep i) solution to less than 20° C.; preferably about −10° C. to about0° C.

Then, adding an antisolvent to the step ii) reaction solution andstirring the solution for a period of about 1 hour to about 2 hours toprecipitating out the crystalline compound of Formula XVIII. Then, theresultant compound of Formula XVIII can be recovered by any conventionaltechniques known in the art, for example filtration and the resultantproduct may optionally be further dried.

The suitable anti-solvent for precipitating the compound of FormulaXVIII include, but is not limited to aliphatic hydrocarbons, cyclichydrocarbons, ethers and the like and water and mixture thereof. Thealiphatic hydrocarbons include, but are not limited to n-hexane,n-heptane, n-pentane and the like; cyclic hydrocarbons include, but arenot limited to cyclopentane, cyclohexane and the like; ethers include,but are not limited to methyl tertiary butyl ether, diethyl ether andthe like; and water and mixture thereof; preferable water.

In another embodiment, the present invention provides crystallinecompound of Formula XVIII characterized by a powder X-Ray diffraction(PXRD) pattern substantially in accordance with FIG. 9.

The compound of Formula XVIII obtained according to the processdescribed just as above can be converted in to a diastereomeric mixtureof compound of Formula XIXa and Formula XIXb using a reducing agent.

The reducing agent used herein includes but is not limited to sodiumborohydride with cerium trichloride, lithium tri-tert-butoxyaluminiumhydride; preferable sodium borohydride with cerium trichloride.

The reduction of compound of Formula XVIII can be carried out in asuitable organic solvent. The suitable organic solvent includes but isnot limited to alcohols, ethers and the like and mixture thereof. Thealcohols include, but are not limited to methanol, ethanol, propanol,isopropanol and the like; ethers include, but are not limited totetrahydrofuran, dimethyl ether and the like and mixture thereofpreferably methanol. The reduction of compound of Formula III is carriedout at a temperature of about −15° C. to about 35° C.; preferably atabout −10 to 0° C.

After completion of the reaction, the reaction mass may be quenched withacetic acid and compound of Formula XIX may be extracted with a waterimmiscible organic solvent such as ethyl acetate, methylene chloride,methyl tertiary butyl ether; preferable ethyl acetate and distilling outthe water immiscible organic solvent under vacuum to obtain adiastereomeric mixture of compound of Formula XIXa and Formula XIXb asresidue. The residue obtained is purified by a solvent crystallizationmethod to isolate the diastereomeric mixture of compound of Formula XIXaand Formula XIXb as a crystalline solid.

In an embodiment, the diastereomeric mixture of compound of Formula XIXaand Formula XIXb may be purified by recrystallization using a solvent toobtain corresponding pure compounds as a crystalline solid.

In another embodiment, the present invention provides a process for thepreparation of diastereomeric mixture of compound of Formula XIXa andFormula XIXb as a crystalline solid, comprising:

-   -   i) providing a solution of diastereomeric mixture of a compound        of Formula XIXa and Formula XIXb in a suitable solvent,    -   ii) cooling the step i) solution to less than 10° C.,    -   iii) adding an anti-solvent to the step ii) solution, and    -   iv) isolating the crystalline compound of Formula XIX; wherein        the suitable solvent is selected from the group comprising        alcohols, ketones, esters, nitriles and the like and mixture        thereof; and the anti-solvent is selected from the group        comprising aliphatic hydrocarbons, cyclic hydrocarbons, ethers        and the like and water and mixture thereof.

The step i) of providing a solution of diastereomeric mixture of acompound of Formula XIXa and Formula XIXb includes heating to dissolvethe diastereomeric mixture of Formula XIXa and XIXb obtained by theprocess described above, in a suitable solvent at a temperature of about25° C. to about reflux temperature; preferably at about 25° C. to about35° C.

The suitable solvent for dissolving a diastereomeric mixture of acompound of Formula XIXa and Formula XIXb include, but is not limited toalcohols, ketones, esters, nitriles and the like and mixtures thereof.The alcohols include, but are not limited to methanol, ethanol,propanol, isopropanol and the like; ketones include, but are not limitedto acetone, methyl isobutyl ketone, methyl ethyl ketone and the like;esters include, but are not limited to methyl acetate, ethyl acetate,isopropyl acetate and the like; nitriles include, but are not limited toacetonitrile, propionitrile and the like and mixture thereof; preferablymethanol.

The step ii) process involves cooling the step a) resulted solution toless than 10° C.; preferably about 0° C. to about 5° C.

The step iii) process involves addition of an anti-solvent to the abovestep ii) reaction solution and stirring the solution for about 2 hoursto precipitate the crystalline diastereomeric mixture of a compound ofFormula XIXa and Formula XIXb. Then, the resultant pure diastereomericmixture of compound of Formula XIXa and XIXb can be recovered by anyconventional techniques known in the art, for example filtration and theresultant product may optionally be further dried.

The suitable anti-solvent for precipitating the diastereomeric mixtureof a compound of Formula XIXa and Formula XIXb include, but is notlimited to aliphatic hydrocarbons, cyclic hydrocarbons, ethers and thelike and water and mixture thereof. The aliphatic hydrocarbons include,but are not limited to n-hexane, n-heptane, n-pentane and the like;cyclic hydrocarbons include, but are not limited to cyclopentane,cyclohexane and the like; ethers include, but are not limited to methyltertiary butyl ether, diethyl ether and the like; and water and mixturethereof; preferable water.

In another embodiment, the present invention provides crystallinediastereomeric mixture of a compound of Formula XIXa and Formula XIXbcharacterized by a powder X-Ray diffraction (PXRD) pattern substantiallyin accordance with FIG. 10.

The diastereomeric mixture of compound of Formula XIXa and Formula XIXbobtained according to the process described as above can be converted into diastereomeric mixture of compound of Formula XVIa and Formula XVIbby epoxidation and followed by oxidation.

The epoxidizing agent used herein includes but is not limited tom-chloroperbenzoic acid, VO(acac)₂, hydrogen peroxide and the like;preferable m-chloroperbenzoic acid.

The epoxidation is carried out in a suitable organic solvent such asmethylene chloride at a temperature of about 0° C. to about 50° C.;preferably at about 0° C. to about 35° C.

After completion of the reaction, diastereomeric mixture of compound ofFormula XXa and Formula XXb may be isolated by extracting the reactionmass with water immiscible organic solvent such as ethyl acetate,methylene chloride, methyl tertiary butyl ether; preferable methylenechloride and distilling out the water immiscible organic solvent undervacuum to obtain a diastereomeric mixture of compound of Formula XXa andFormula XXb as residue.

Then the obtained diastereomeric mixture of compound of Formula XXa andFormula XXb can be converted in to a diastereomeric mixture of compoundof Formula XVI and Formula XVIa in presence of a suitable oxidizingagent.

The oxidizing agent used herein include but is not limited toDess-Martin periodinane, tetrapropylammonium perruthenate with4-methylmorpholine-N-oxide; preferable Dess-Martin periodinane.

The oxidation is carried out in a suitable organic solvent such asacetonitrile at a temperature of about 0° C. to about 50° C.; preferablyat about 25 to about 30° C.

After completion of the reaction, the diastereomeric mixture of compoundof Formula XVI and Formula XVIa may be extracted with water immiscibleorganic solvent such as ethyl acetate, methylene chloride, methyltertiary butyl ether; preferable ethyl acetate and distilling the waterimmiscible organic solvent under vacuum to obtain diastereomeric mixtureof compound of Formula XVI and Formula XVIa as residue.

The compound of Formula XVI may be separated from the obtaineddiastereomeric mixture of compound of Formula XVI and Formula XVIa bysubjecting the mixture to column chromatography by eluting with ethylacetate and cyclohexane solvent system and the product containingsolvent fractions are collected and distilled under vacuum to obtaincompound of Formula XVI as a residue.

The resulting compound of Formula XVI, obtained by the aforementionedprocess, may have a chemical purity of at least about 99%, as measuredby HPLC and about 0.5 to 1% of compound of Formula XVIII as measured byHPLC.

In another embodiment, the present invention provides an improvedprocess for the preparation of compound of Formula XVI, comprisingpurifying the compound of Formula XVI as obtained by the processdescribed above or may be obtained by any known process, as a startingmaterial or as an intermediate by solvent and anti-solvent method toobtain pure compound of Formula XVI which is having chemical purity ofat least about 99.9%, as measured by HPLC and less than about 0.1% ofFormula XVIII as measured by HPLC.

In another embodiment, the present invention provides a process for thepurification of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI, comprising:

-   -   i) providing a solution of tert-butyl        ((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamate        of Formula XVI in a suitable solvent,    -   ii) cooling the step i) solution to less than 5° C.,    -   iii) optionally adding seed compound of Formula XVI to the        step ii) solution, and    -   iv) isolating the pure compound of Formula XVI; wherein the        suitable solvent is selected from aliphatic hydrocarbons, cyclic        hydrocarbons, ethers and the like and mixture thereof.

In another embodiment, the present invention provides a process forpreparation of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI having less than 0.1% of compound of Formula XVIII asmeasured by HPLC, comprising purifying the compound of Formula XVI bythe process described above.

The step i) of providing a solution of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI includes heating to dissolve the compound of Formula XVIobtained by the process described as above, in a suitable solvent at atemperature of about 25° C. to about reflux temperature; preferably atabout 25° C. to about 35° C.

The suitable solvent for dissolving compound of Formula XVI include, butnot limited to aliphatic hydrocarbons, cyclic hydrocarbons, ethers andthe like and mixtures thereof. The aliphatic hydrocarbons include, butare not limited to n-hexane, n-heptane, n-pentane and the like; cyclichydrocarbons include, but are not limited to cyclopentane, cyclohexaneand the like; ethers include, but are not limited to methyl tertiarybutyl ether, diethyl ether and the like and mixture thereof preferablyn-heptane.

The resultant solution may be cooled to less than 5° C., preferablyabout −10° C. to 0° C. Optionally the solution may be seeding with aseed compound of Formula XVI to precipitating out the crystallinecompound of Formula XVI. The precipitated crystalline compound ofFormula XVI may be isolated by methods known in the art, for examplefiltration followed by drying at suitable temperatures.

In another embodiment, the present invention provides crystallinetert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI characterized by a powder X-Ray diffraction (PXRD)pattern substantially in accordance with FIG. 8.

In another embodiment, the present invention provides compound ofFormula XVI containing less than 0.1% of compound of Formula XVIII asmeasured by HPLC.

In another embodiment, the present invention provides an improvedprocess for the preparation of carfilzomib, comprising preparing thetert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI as process described above, and converting the tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI in to carfilzomib by any process known in the art or bythe process described in the above specification.

In another embodiment, the present invention provides a process for thepreparation of carfilzomib, comprising providing a compound of FormulaXVI as obtained by the process described above, as a starting materialor as an intermediate, where the purity of the carfilzomib having atleast about 99% and less than 0.1% of compound of Formula XVIII asmeasured by HPLC, preferably at least about 99.5% and less than 0.05% ofcompound of Formula XVIII as measured by HPLC.

The X-Ray powder diffraction can be measured by an X-ray powderdiffractometer equipped with a Cu-anode ([k]=1.54 Angstrom), X-raysource operated at 30 kV, 15 mA. Two-theta calibration is performedusing an NIST SRM 640c Si standard. The sample was analyzed using thefollowing instrument parameters: measuring range=3-45° 2θ; stepwidth=0.020°; and scan speed=5°/minute.

As used herein, the pharmaceutical acceptable salts include acidaddition salts formed with inorganic acids or with organic acids. Theinorganic acids may be selected from hydrochloric acid, hydrobromicacid, sulfuric acid, phosphoric acid, nitric acid, sulfamic acid, andthe like; organic acids may be selected from acetic acid, oxalic acid,fumaric acid, succinic acid, tartaric acid, salicylic acid, benzoicacid, glycolic acid, methane sulfonic acid, ethanesulfonic acid,benzenesulfonic acid, p-toluenesulfonic acid, lactic acid, maleic acid,malonic acid, malic acid and the like.

In another embodiment, the present invention provides carfilzomib or apharmaceutically acceptable salt thereof and its intermediates, obtainedby the above process, as analyzed using high performance liquidchromatography (“HPLC”) with the conditions are tabulated below:

Column Halo C18 (100 × 4.6) mm, 2.7 μm Column temperature 35° C. Mobilephase Mixture of buffer and Acetonitrile (30:70) v/v Buffer Dipotassiumhydrogen phosphate Diluent Water and Acetonitrile (30:70) v/v Flow rate1.0 mL/min Wavelength By UV at 210 nm Injection Volume 10 μL ElutionGradient

In another embodiment, the present invention provides a pharmaceuticalcomposition, comprising carfilzomib or a pharmaceutically acceptablesalt thereof prepared by the processes of the present invention and atleast one pharmaceutically acceptable excipient.

Such pharmaceutical composition may be administered to a mammalianpatient in any dosage form, e.g., injectable solution, solid, liquid,powder etc.

EXAMPLES

The following non limiting examples illustrate specific embodiments ofthe present invention. They are not intended to be limiting the scope ofthe present invention in any way.

Example 1: Preparation of Compound of Formula IV

A mixture of N-boc-L-leucine (45 g, 1.05 eq) and toluene (500 ml) washeated to 50-55° C. and stirred for 30 min at same temperature. Thereaction mass was distilled completely under vacuum at less than 55° C.to obtain residue. To the obtained residue dimethyl formamide (250 ml)was charged at 25-30° C. and allowed to cool to 2-6° C. To the reactionmass HOBt (2.4 g, 0.1 eq), PyBOP (107 g, 1.2 eq) and L-phenyl alaninebenzyl ester hydrochloride (50 g, 1 eq) and diisopropyl ethyl amine (89g, 4 eq) were sequentially added at 2-6° C. and stirred for 5 min atsame temperature. Then the reaction mass was heated to 25-30° C. andstirred for 2-3 hr at same temperature. After completion of thereaction, reaction mass was quenched in to water (2500 ml) at 25-30° C.and stirred for 3-4 hr at same temperature. Precipitated solid wasfiltered, washed with water (250 ml) and dried to get the titlecompound. Yield: 77.5 g; PXRD: FIG. 1; DSC: endothermic peak at about104° C.; Chemical purity by HPLC: 99.97%; HOBt: Not detected, PyBOP:0.01% and tris(pyrrolidino phosphine) oxide: Not detected by HPLC.

Example 2: Preparation of Compound of Formula VII

A mixture of methylene chloride (90 ml) and trifluoro acetic acid (210ml) was allowed to cool to 2-6° C. and compound of Formula IV (100 g, 1eq) was added at same temperature. Then the reaction mass was heated to25-30° C. and stirred for 2 hr at same temperature. To the reaction massmethylene chloride (1.5 lit) was added and pH adjusted to 7-8 with 20%sodium carbonate at 25-30° C. and stirred for 20 min at sametemperature. Separated the organic layer and washed with water (300 ml)and 10% sodium chloride (300 ml) sequentially. Organic layer wasseparated and concentrated under vacuum at below 35° C. to obtainresidue. The obtained residue was dissolved in dimethyl formamide (500ml) and allowed to cool to 2-6° C. To the reaction mass HOBt (2.9 g, 0.1eq), PyBOP (133.5 g, 1.2 eq), N-boc-homo phenyl alanine (59.7 g, 1 eq)were added slowly at 2-6° C. To the reaction mass HOBt (2.9 g, 0.1 eq),PyBOP (133.5 g, 1.2 eq), N-boc-homo phenyl alanine (59.7 g, 1 eq) anddiisopropyl ethyl amine (110.5 g, 4 eq) were added slowly at 2-6° C.Then the reaction mass was heated to 25-30° C. and stirred for 2-3 hr atsame temperature. After completion of the reaction, reaction mass wasquenched in to water (Slit) at 25-30° C. and stirred for 2-3 hr at sametemperature and the precipitated solid was filtered, washed with water(500 ml) and dried to get the title compound. Yield: 130 g; PXRD: FIG.2; DSC: endothermic peak at about 150° C.; Chemical purity by HPLC:99.97%; HOBt: 0.1%, PyBOP: Not detected and tris(pyrrolidino phosphine)oxide: 0.02% by HPLC.

Example 3: Preparation of Compound of Formula VIII

A mixture of methanol (150 ml), methylene chloride (150 ml), compound ofFormula VII (30 g) and 10% Pd/C (6 g) were charged in to 2 lit autoclave at 25-35° C. and purged hydrogen gas at 25-30° C. for a period of36 hr. After completion of the reaction, filtered the reaction mass andfilterate was distilled under vacuum at below 40° C. To the obtainedcompound n-heptane (120 ml) was added at 25-35° C. and stirred for 1-2hr at same temperature. The solid obtained was filtered and dissolved inethyl acetate (120 ml) at 25-35° C. The obtained solution was added into n-heptane (450 ml) at 25-35° C. and stirred for 2 hr at sametemperature. Precipitated solid was filtered, washed with n-heptane (90ml) and dried to get the title compound. Yield: 24 g; PXRD: FIG. 3; DSC:endothermic peak at about 64° C.; Chemical purity by HPLC: 97.2%.

Example 4: Preparation of Compound of Formula X

A mixture of methylene chloride (105 ml) and[(1S)-3-Methyl-1-[[(2R)-2-methyloxiranyl] carbonyl]butyl]carbamic acid1,1-dimethylethyl ester (7.5 g, 1 eq) was allowed to cool to 2-6° C. Tothe reaction mass trifluoroacetic acid (15 ml) was added at sametemperature. Then the reaction mass was heated to 25-30° C. and stirredfor 2 hr at same temperature. After completion of reaction, reactionmass was distilled completely under vacuum at below 35° C. and theobtained residue was dissolved in dimethyl formamide (30 ml).

In another reaction flask a mixture of dimethyl formamide (45 ml) andcompound of Formula VIII (15 g, 1 eq) was allowed to cool to 2° C. to 6°C. To the reaction mass HOBt (0.4 g, 0.1 eq), PyBOP (23.2 g), dimethylformamide solution of(2S)-2-Amino-4-methyl-1-[(2R)-2-methyloxiranyl]-1-pentanonetrifluoroacetate(30 ml) and diisopropyl ethyl amine (14.4 g, 4 eq) was slowly addedsequentially at 2° C. to 6° C. and stirred for 2-4 hr at sametemperature. After completion of the reaction, reaction mass wasquenched in to water (750 ml) at 25-30° C. and stirred for 2-3 hr atsame temperature. Precipitated solid was filtered and washed with water(75 ml) to obtain crude compound of Formula X.

The obtained crude compound of Formula X was dissolved in ethyl acetate(225 ml) at 25-35° C. and heated to reflux for 30 min. filtered theundissolved material and reaction mass was allowed to cool to 2-6° C.Precipitated solid was filtered, washed with chilled ethyl acetate (30ml) and dryed to get the title compound. Yield: 14 g; PXRD: FIG. 4; DSC:endothermic peak at about 151.7° C. and exothermic peak at about 164°C.; Chemical purity by HPLC: 97.0%.

Example 5: Preparation of Carfilzomib Maleate Salt

A mixture of methylene chloride (140 ml) and compound of Formula X (14g, 1 eq) was allowed to cool to 2-6° C. and trifluoroacetic acid (84 ml)was added at same temperature and stirred for 2-3 hr at sametemperature. After completion of reaction, reaction mass was distilledcompletely under vacuum at below 35° C. and the obtained compound wasslurred in n-heptane (70 ml) at 25-35° C. Filtered the solids and washedwith n-heptane (70 ml) to obtain trifluoro acetic acid salt of FormulaXI. PXRD: FIG. 5; DSC: endothermic peak at about 115° C.; or thereaction mass was basified and isolated the compound of Formula XI asits free base. PXRD: FIG. 6; DSC: exothermic peaks at about 76.8° C. and141.8° C. A mixture of dimethyl formamide (42 ml) and 2-morpholinoacetic acid of Formula XII (3.73 g) was allowed to cool to 2-6° C. Tothe reaction mass HOBt (0.27 g, 0.1 eq), PyBOP (12.6 g, 1.2 eq), FormulaXI free base (dissolved in 28 ml dimethyl formamide) and diisopropylethyl amine (10.34 g, 4 eq) were slowly added sequentially at 2° C. to6° C. and stirred for 2-4 hr at same temperature. After completion ofthe reaction, reaction mass was quenched in to water (700 ml) at 25-30°C. and stirred for 2-3 hr at same temperature. Precipitated solid wasfiltered, washed with water (75 ml). The obtained compound was dissolvedin ethyl acetate (700 ml), washed with 5% sodium bisulphate (2×140 ml),5% sodium bicarbonate (2×140 ml) and water (140 ml) sequentially.Organic layer was separated and passed through silicycle-M 60 silica gelbed and compound containing fractions were collected and distilledcompletely under vacuum at 25-35° C. to obtaine residue. The obtainedresidue was dissolved in a mixture of acetonitrile (70 ml) andtetrahydrofuran (35 ml) at 25-35° C. and stirred for clear solution. Tothe reaction mass maleic acid (2.32 g) was added at 25-30° C. andstirred for 30 min at same temperature. To the reaction massacetonitrile (70 ml) was charged and stirred for 1-2 hr at 25-30° C.Precipitated solid was filtered, washed with acetonitrile (70 ml) anddried. To the obtained compound n-propanol (210 ml) was added and heatedto reflux for 30-60 min. Reaction mass was allowed to cool to 25-35° C.Precipitated solid was filtered, washed with chilled n-propanol (28 ml)and dried to get crystalline maleate salt. Yield: 8 g; Chemical purityby HPLC: 99.8%; PXRD: FIG. 7; DSC: Endothermic peak at 185.4° C.; TGA:No weight loss; HOBt: 0.15%, PyBOP: Not detected and tris(pyrrolidinophosphine) oxide: 0.05% by HPLC.

Example 6: Preparation of Compound of Formula XIV

A mixture of methylene chloride (60 ml) and trifluoro acetic acid (240ml) was allowed to cool to 2-6° C. To the reaction mass compound ofFormula VII (100 g, 1 eq) was added at same temperature. Then thereaction mass was heated to 25-30° C. and stirred for 2 hr at sametemperature. To the reaction mass methylene chloride (1.5 lit) was addedand pH adjusted to 7-8 with 20% sodium carbonate at 25-30° C. andstirred for 20 min at same temperature. Separated the organic layer andwashed with water (300 ml) and 10% sodium chloride (300 ml)sequentially. Organic layer was separated and concentrated under vacuumat 25-35° C. to obtain residue. The obtained residue was dissolved indimethyl formamide (500 ml) and allowed to cool to 2-6° C. To thereaction mass HOBt (2.2 g, 0.1 eq), PyBOP (99.2 g, 1.2 eq), morpholineacetic acid (29.5 g, 1.2 eq) and diisopropyl ethyl amine (82.1 g, 4 eq)were slowly added sequentially at 2-6° C. Then the reaction mass washeated to 25-30° C. and stirred for 2-3 hr at same temperature. Aftercompletion of the reaction, reaction mass was quenched in to water (514)at 25-30° C. and stirred for 2 hr at same temperature and the solidprecipitated was filtered, washed with water (500 ml) and dried to getthe title compound. Yield: 94 g; Chemical purity by HPLC: 97.6%; HOBt:0.35%, PyBOP: 0.01% and tris(pyrrolidino phosphine) oxide: 0.04% byHPLC.

Example 7: Preparation of Compound of Formula XV

Compound of Formula XIV (100 g) was dissolved in methanol (4.5 lit) at25-30° C. To the reaction mass ammonium formate (38.5 g dissolved in 500ml methanol) and palladium on carbon (20 g) were added and stirred for 2hr at same temperature. After completion of the reaction, filtered thereaction mass and filterate was distilled under vacuum at below 45° C.to obtain residue. To the obtained residue water (Hit) was added at25-30° C. and stirred for 2-3 hr at same temperature. The solid wasfiltered, washed with acetone (500 ml) and dried. To the obtained solidn-propanol (3 lit) was added and heated to reflux for 1 hr. Then thereaction mass was allowed to cool to 25-30° C. and stirred for 2-4 hr atsame temperature. Precipitated solid was filtered, washed withn-propanol (200 ml) and dried to get the title compound. Yield: 77 g;Chemical purity by HPLC: 99.7%.

Example 8: Preparation of Carfilzomib Maleate Salt

A mixture of methylene chloride (250 ml) and[(1S)-3-Methyl-1-[[(2R)-2-methyloxiranyl]carbonyl]butyl]carbamic acid1,1-dimethylethyl ester (50 g, 1 eq) was allowed to cool to 2-6° C. Tothe reaction mass trifluoroacetic acid (100 ml) was added at sametemperature. Then the reaction mass was heated to 25-30° C. and stirredfor 2 hr at same temperature. After completion of reaction, reactionmass was distilled completely under vacuum at below 35° C. and theobtained residue was dissolved in acetonitrile (500 ml).

In another reaction flask a mixture of acetonitrile (4500 ml) andcompound of Formula XV (100 g, 1 eq) was allowed to cool to −10° C. to−5° C. To the reaction mass HOBt (38.1 g, 0.1 eq), PyBOP (146.8 g, 1.2eq), acetonitrile solution of(2S)-2-Amino-4-methyl-1-[(2R)-2-methyloxiranyl]-1-pentanonetrifluoroacetate(500 ml) and diisopropyl ethyl amine (91.2 ml, 4 eq) were addedsequentially at −10° C. to −5° C. and stirred for 3-4 hr at sametemperature. After completion of the reaction, reaction mass wasdistilled completely under vacuum at below 35° C. to obtain residue andthe obtained residue was dissolved in ethyl acetate and washed the clearsolution with 5% sodium bicarbonate (3×100 ml), water (Hit), 5% sodiumchloride (Hit) sequentially. Organic layer was separated and passedthrough silica gel bed and the product containing fractions werecollected and distilled completely under vacuum at below 35° C. toobtain residue. The obtained residue was dissolved in a mixture ofacetonitrile (250 ml) and tetrahydrofuran (250 ml) at 25-30° C. To thereaction mass maleic acid (20.5 g) was added at 25-30° C. and stirredfor 30 min at same temperature. To the reaction mass acetonitrile (500ml) was charged and stirred for 1-2 hr at 25-30° C. The solid obtainedwas filtered, washed with acetonitrile (1.5 lit) and dried. To theobtained compound n-propanol (Hit) was added and heated to reflux for 10min. Then the reaction mass was allowed to cool to 2-6° C. Precipitatedsolid was filtered, washed with chilled n-propanol (Hit) and dried toget the title compound. Yield: 100 g; PXRD: FIG. 7; Chemical purity byHPLC: 99.8%; HOBt: 0.15%, PyBOP: Not detected and tris(pyrrolidinophosphine) oxide: 0.05% by HPLC.

Example 9: Preparation of Amorphous Form of Carfilzomib

A mixture of methylene chloride (180 ml) and carfilzomib maleate salt (6g) was allowed to cool to 2-6° C. To the reaction mass sodiumbicarbonate solution (1.27 g dissolved in 60 ml water) was added slowlyat 2-6° C. and stirred for 10 min at same temperature. Organic layer wasseparated and washed with sodium bisulphate (2×60 ml) and water (2×60ml) sequentially. Organic layer was separated and distilled under vacuumcompletely to obtain residue. The obtained residue was dissolved in amixture of ethyl acetate (90 ml) and methylene chloride (12 ml) andpassed the solution through neutral silica bed and separated the productcontaining fractions and distilled completely under vacuum at below 40°C. to obtain residue. The obtained residue was dissolved in methanol (42ml) at 25-30° C. Then the methanol solution was slowly added in to precooled water (420 ml) at 4-10° C. and stirred for 1 hr at sametemperature. Precipitated solid was filtered, washed with water (60 ml)and dried to get the title compound. Yield: 2.4 g; Chemical purity byHPLC: 99.8%; HOBt: Not detected, PyBOP: Not detected, tris(pyrrolidinophosphine) oxide: Not detected, Formula 28: 0.02%, Formula 29 to Formula36: Not detected, Formula 37: 0.02%, Formula 38: Not detected, Formula39: Not detected, Formula 40: 0.02% and Formula 41: Not detected byHPLC.

Example 10: Preparation of tert-butyl ((2S)-1-(methoxy (methyl)amino)-4-methyl-1-oxopentane-2-yl) carbamate of Formula XVII

A mixture of N-Boc-L-Leucine monohydrate (216 g) and toluene (2 lit) washeated to 45-50° C. and was distilled completely under vacuum at sametemperature to obtain a residue. To the obtained residue methylenechloride (1 lit) was added at 25-30° C. and allowed to cool to −10° C.to −5° C. To the reaction mass PyBOP (584 g), HOBt (128 g), N,O-dimethylhydroxyl amine hydrochloride (168 g) and diisopropylethylamine (690 ml)were added and allowed to stir at same temperature. After completion ofthe reaction, reaction mass was washed with 8% sodium bicarbonatesolution (2 lit), water (2 lit), 10% sodium chloride solution (2 lit)sequentially. Organic layer was separated and distilled under vacuumcompletely and followed by co-distilled with cyclohexane (500 ml) toobtain residue. To the obtained residue cyclohexane (2 lit) was addedand stirred for 30 min at 25-30° C. Filtered the reaction mass and thefilterate was concentrated under vacuum to obtain a residue. Theobtained residue was dissolved in cyclohexane (1 lit) and passed throughneutral alumina column. Concentrated the product containing columnfractions completely under vacuum to obtain residue and the obtainedresidue was dissolve in n-hexane (100 ml) at 25-30° C. and allowed tocool to −15 to −10° C. and stirred for 2 hr at same temperature.Filtered the un-wanted solids and concentrated the filterate undervacuum at 45-50° C. to obtain title compound. Yield: 210 g

Example 11: Preparation of tert-butyl ((4S)-2,6-dimethyl-3-oxohept-1-en-4-yl))carbamate of Formula XVIII

A mixture of compound of Formula XVII (100 g) and toluene (1500 ml) washeated to 75-80° C. and was distilled completely under vacuum at sametemperature to obtain residue. The obtained residue was dissolved intetrahydrofuran (100 ml) at 25-30° C. In another reaction flaskisopropenyl magnesium bromide (2.19 lit) was charged at 25-30° C. andslowly added the above tetrahydrofuran solution over 2 hr at 25-40° C.and stirred for 45 min at same temperature. After completion of thereaction, quenched the reaction mass in to 15% ammonium chloride (1.5lit) at 0-5° C. and organic layer was separated and concentrated undervacuum at below 40° C. to obtain residue. The obtained residue waspurified by silicycle silica by using ethyl acetate and cyclohexanesolvent system. Product containing solvent fractions were combined andconcentrated under vacuum at below 40° C. to obtain residue. Theobtained residue was dissolved in acetone (100 ml) at 25-30° C. andallowed to cool to −5 to 0° C. To the clear solution water (1.5 lit) wasadded slowly at −5 to 0° C. Precipitated solid was filtered, washed withwater (100 ml) and dried to get the title compound as a crystallinesolid. Yield: 72 g; PXRD: FIG. 9; Chemical purity by HPCL: 99.44%;Chiral purity by HPLC: 99.73%.

Example 12: Preparation of tert-butylN-[(3R/S,4S)-3-hydroxy-2,6-dimethylhept-1-en-4-yl]carbamate of FormulaXIX

A mixture of compound of Formula XVIII (115 g) and methanol (500 ml) wasallowed to cool to 0-5° C. To the reaction mass cerium (III) chlorideheptahydrate solution (203 g dissolved in 500 ml methanol) was addedslowly at 0-5° C. Then the reaction mass was allowed to cool −5 to 0° C.and sodium borohydride (10.2 g) was added in lot wise over 1 hr at sametemperature. After completion of the reaction, acetic acid (20 ml) wasadded drop wise at same temperature and concentrated reaction mass undervacuum at below 40° C. to obtain a solid. The obtained solid wasdissolved in ethyl acetate (1 lit) and washed with water (500 ml) and10% sodium chloride solution (500 ml) sequentially. Organic layer wasseparated and concentrated under vacuum at below 40° C. to obtain titlecompound as a solid. The obtained solid was dissolved in methanol (100ml) at 25-30° C. and allowed to cool to 0-5° C. To the reaction masswater (150 ml) was added at 0-5° C. Precipitated solid was filtered,washed with water (100 ml) and dried to get the title compound as acrystalline solid. Yield: 95 g; PXRD: FIG. 10; Chemical purity by HPLC:99.48%, Chiral purity by HPLC: 99.99%.

Example 13: Preparation of tert-butylN-[(1R/S,2S)-1-((2R/S)-2-methyloxirane-2-yl)-1-hydroxy-4-methylpentan-2-yl]carbamateof Formula XX

A mixture of compound of Formula XIX (20 g) and methylene chloride (200ml) was allowed to cool to 0-5° C. To the reaction mass mCPBA (22.6 g)was added in lot wise at 0-5° C. and heated to 25-30° C. Aftercompletion of the reaction, reaction mass was allowed to cool to 0-5° C.and solid was filtered. Then the product containing filterate was washedwith 8% sodium bicarbonate solution (200 ml) and 10% sodium bisulphatesolution (200 ml). Organic layer was separated and concentrated undervacuum at below 40° C. to obtain title compound. Yield: 17 g.

Example 14: Preparation of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo pentan-2-yl)carbamate of Formula XVI

Compound of Formula XX (16 g) was dissolved in acetonitrile (80 ml) at25-30° C. To the reaction mass a mixture of acetonitrile (80 ml) andDess-Martin Periodinane (37.3 g) were added over a period of 1 hr at0-5° C. Then the reaction mass was heated to 25-30° C. and stirred for 2hr at same temperature. After completion of the reaction, reaction masswas quenched in to 8% sodium bicarbonate solution (160 ml) at 0-5° C.and extracted with ethyl acetate. Ethyl acetate layer was concentratedunder vacuum at below 40° C. to obtain oily mass. The obtained oily masswas purified by column chromatography using a mixture of 0.5% ethylacetate and cyclohexane as an eluent. Then the product containingsolvent fractions were combined and concentrated under vacuum at below40° C. to obtain title compound as residue. Chemical purity by HPLC:99.0%; Compound of Formula XVIII by HPLC: 0.5%.

The obtained residue was dissolved in n-heptane (4 ml) at 25-30° C. andstirred for 10 min at same temperature. Reaction mass was allowed tocool to −5 to 0° C. and stirred for 30 min at same temperature, to thereaction mass seed compound of Formula XVI (16 mg) was added at sametemperature. Precipitated solid was filtered and dried to get the titlecompound as a crystalline solid. Yield: 4.5 g; PXRD: FIG. 8; Chemicalpurity by HPLC: 99.88%, Compound of Formula XVIII by HPLC: 0.05%, Chiralpurity by HPLC: 100%.

Comparative Example 1: Preparation of Compound of Formula IV

A mixture of acetonitrile (900 ml), N-boc-L-leucine (19.8 g, 1 eq),L-phenyl alanine benzyl ester hydrochloride (25 g, 1 eq) and diisopropylethyl amine (44.2 g, 4 eq) were charged in to a reaction flask at 25-30°C. and stirred for 10 min at same temperature. Then the reaction masswas allowed to cool to 0° C. and HOBt (18.5 g, 1.6 eq), PyBOP (71.3 g,1.6 eq) were added in lot wise over 5 min at same temperature andstirred under nitrogen for overnight at same temperature. Aftercompletion of reaction, reaction mass was distilled completely undervacuum and the obtained crude was dissolved in ethyl acetate (500 ml),washed with saturated sodium bicarbonate solution, water followed bysodium chloride solution. Organic layer was dryed with magnesiumsulphate and distilled under vacuum to obtain title compound. Yield: 25g; Chemical purity by HPLC: 88.12%; HOBt: 4.1%, PyBOP: Not detected andtris(pyrrolidino phosphine) oxide: 5.41% by HPLC.

Comparative Example 2: Preparation of Compound of Formula VII

A mixture of 70% trifluoro acetic acid/methylene chloride (150 ml) wasallowed to cool to 0° C. To the reaction mass compound of Formula IV (25g, 1 eq) was added at same temperature. Then the reaction mass washeated to 25-30° C. and stirred for 2 hr at same temperature. Aftercompletion of reaction, distilled the reaction mass completely undervacuum and the obtained trifluoroacetic acid salt of Formula V wasdissolved in acetonitrile (550 ml). To the reaction mass N-boc-homophenyl alanine (25 g, 1 eq) and diisopropyl ethyl amine (27.5 g, 4 eq)were added at 25-30° C. Reaction mass was allowed to cool to 0° C. andHOBt (11.5 g, 1.6 eq), PyBOP (44.4 g, 1.6 eq) were added in lot wiseover 5 min at same temperature and stirred for overnight under nitrogenat 25-30° C. Then the reaction mass was allowed to cool to 0° C. and thesolid obtained was filtered, washed with chilled acetonitrile to get thetitle compound. Yield: 24.8 g; Chemical purity by HPLC: 89.35%; HOBt:9.9%, PyBOP: 0.02% and tris(pyrrolidino phosphine) oxide: 0.24% by HPLC.

Comparative Example 3: Preparation of Compound of Formula XIV

A mixture of 80% trifluoro acetic acid/methylene chloride (12 ml) andcompound of Formula VII (0.25 g, 1 eq) were combined in a reaction flaskat 25-30° C. and stirred for 1 hr at same temperature. After completionof reaction, reaction mass was distilled completely under vacuum and theobtained oily trifluoroacetic acid salt of Formula VIII was dissolved indimethyl formamide (6 ml). To the reaction mass morpholine acetic acid(0.07 gm) and diisopropyl ethyl amine (0.5 g, 10 eq) were added at25-30° C. Then reaction mass was allowed to cool to 0° C. and PyBOP (0.3g, 1.6 eq) was added in lot wise for 5 min at same temperature. Reactionmass was heated to 25-30° C. and stirred for overnight under nitrogen.After completion of reaction, reaction mass was diluted with brinesolution and extracted with ethyl acetate and washed with saturatedsodium bicarbonate solution, water followed by sodium chloride solution.Organic layer was separated and distilled under vacuum to obtain titlecompound. Yield: 0.19 g; Chemical purity by HPLC: 92.14%; HOBt: 2.03%,PyBOP: 0.24% and tris(pyrrolidino phosphine) oxide: 3.4% by HPLC.

Comparative Example 4: Preparation of Compound of Formula XV

Compound of Formula XIV (0.19 g) was dissolved in 1:1 mixture ofmethanol and ethyl acetate (5 ml) at 25-30° C. To the reaction mass 10%Pd/C (0.05 g) was added and stirred under hydrogen atmosphere for 2 hrat same temperature. After completion of reaction, filtered the reactionmass through hyflo bed and filterate was distilled under vacuum toobtain title compound. Yield: 0.12 g; Chemical purity by HPLC: 95.90%;HOBt: 0.41% and tris(pyrrolidino phosphine) oxide: 1.42% by HPLC.

Comparative Example 5: Preparation of Carfilzomib

Trifluoroacetic acid salt of Formula IX (0.08 g), acetonitrile (5 ml),compound of Formula XV (01 g, 1 eq), diisopropyl ethyl amine (0.3 g) andHOBt (0.04 g, 1.6 eq) were combined in a reaction flask at 25-30° C.Reaction mass was allowed to cool to 0° C. and PyBOP (0.15 g, 1.6 eq)was added lot wise in 5 min at same temperature. Then the reaction masswas stirred for overnight under nitrogen at 5° C. After completion ofreaction, reaction mass was diluted with brine solution and extractedwith ethyl acetate and the organic layer was washed with saturatedsodium bicarbonate solution, water followed by sodium chloride solution.Organic layer was separated and distilled under vacuum and the obtainedcrude compound was dissolved in methanol and slowly added in to water(100 ml) under rapid stirring at 0° C. Precipitated solid was filteredto get the title compound. Yield: 0.08 g; Chemical purity by HPLC:25.91%; HOBt: 59.34%, PyBOP: 2.04% and tris(pyrrolidino phosphine)oxide: 1.7% by HPLC.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore the above description should notbe constructed as limiting, but merely as exemplifications of preferredembodiments. For example, the functions described above and implementedas the best mode for operating the present invention are forillustration purposes only. Other arrangements and methods may beimplemented by those skilled in the art without departing from the scopeand spirit of this invention. Moreover, those skilled in the art willenvision other modifications within the scope and spirit of thespecification appended hereto.

We claim:
 1. A process for preparation of tert-butyl((2S)-4-methyl-1-((2R)-2-methyloxirane-2-yl)-1-oxo-pentan-2-yl)-carbamateof Formula XVI,

comprising: i) reacting a compound of Formula XVII with alkyl magnesiumhalide to obtain a compound of Formula XVIII,

ii) crystallizing the compound of Formula XVIII from a first solventsystem to obtain a crystalline compound of Formula XVIII; iii) reducingthe crystalline compound of Formula XVIII in the presence of a reducingagent to obtain a diastereomeric mixture of a compound of Formula XIXaand a compound of Formula XIXb,

iv) crystallizing the mixture obtained in step iii) from a secondsolvent system to obtain a mixture of a crystalline compound of FormulaXIXa and a crystalline compound of Formula XIXb; v) epoxidating and thenoxidizing the mixture obtained in step iv) to obtain a diastereomericmixture of a compound of Formula XVI and a compound of Formula XVIa,

vi) separating the compound of Formula XVI from the diastereomericmixture obtained in step v) by chromatography; and vii) crystallizingthe compound of Formula XVI obtained in step vi) from a third solventsystem to obtain a crystalline compound of Formula XVI.
 2. The processof claim 1, wherein the alkyl magnesium halide is isopropenyl magnesiumbromide.
 3. The process of claim 1, wherein the step ii) furthercomprises: a) providing a solution of the compound of Formula XVIII inthe first solvent; b) optionally cooling the step a) solution to lessthan 20° C.; c) adding an anti-solvent to the step b) solution to form amixture; and d) isolating from the mixture obtained in step c) thecrystalline compound of Formula XVIII.
 4. The process of claim 3,wherein the first solvent is selected from the group consisting ofalcohols selected from one of methanol, ethanol, propanol andisopropanol; ketones selected from one of acetone, methyl isobutylketone and methyl ethyl ketone; esters selected from one of methylacetate, ethyl acetate and isopropyl acetate; nitriles selected from oneof acetonitrile and propionitrile; and mixtures thereof.
 5. The processof claim 3, wherein the anti-solvent is selected from the groupconsisting of aliphatic hydrocarbons selected from one of n-hexane,n-heptane and n-pentane; cyclic hydrocarbons selected from one ofcyclopentane and cyclohexane; ethers selected from one of methyltertiary butyl ether and diethyl ether; water; and mixtures thereof. 6.The process of claim 1, wherein the reducing agent is a mixture ofsodium borohydride and cerium trichloride.
 7. The process of claim 1,wherein the step iv) further comprises: a) providing a solution of adiastereomeric mixture of the compound of Formula XIXa and Formula XIXbin the second solvent; b) cooling the solution obtained in step a) toless than 10° C. c) adding an anti-solvent to the solution of step b);and d) isolating from the mixture obtained in step c) the mixture ofcrystalline compound of Formula XIXa and Formula XIXb.
 8. The process ofclaim 7, wherein the second solvent is selected from the groupconsisting of alcohols selected from one of methanol, ethanol, propanoland isopropanol; ketones selected from one of acetone, methyl isobutylketone and methyl ethyl ketone; esters selected from one of methylacetate, ethyl acetate and isopropyl acetate; nitriles selected from oneof acetonitrile and propionitrile; and mixtures thereof.
 9. The processof claim 7, wherein the anti-solvent is selected from the groupconsisting of aliphatic hydrocarbons selected from one of n-hexane,n-heptane and n-pentane; cyclic hydrocarbons selected from one ofcyclopentane and cyclohexane; ethers selected from one of methyltertiary butyl ether and diethyl ether; water; and mixtures thereof. 10.The process of claim 7, wherein the second solvent is methanol and theanti-solvent is water.
 11. The process of claim 1, wherein the step vii)further comprises: a) providing a solution of the compound of FormulaXVI in the third solvent; b) cooling the solution obtained in step a) toless than 5° C.; c) optionally adding a seed compound of Formula XVI tothe solution of step b); and d) isolating from the solution of step b)or step c) the compound of Formula XVI.
 12. The process of claim 11,wherein the third solvent system of step a) is selected from the groupconsisting of aliphatic hydrocarbons selected from one of n-hexane,n-heptane and n-pentane; cyclic hydrocarbons selected from one ofcyclopentane and cyclohexane; ethers selected from one of methyltertiary butyl ether and diethyl ether; and mixtures thereof.
 13. Theprocess of claim 1, further comprising: viii) converting the crystallinecompound of Formula XVI into carfilzomib of Formula I or apharmaceutically acceptable salt thereof.